diff --git a/sdk_container/src/third_party/portage-stable/sys-libs/zlib/Manifest b/sdk_container/src/third_party/portage-stable/sys-libs/zlib/Manifest
index 1db6ff6315..9a8e50982b 100644
--- a/sdk_container/src/third_party/portage-stable/sys-libs/zlib/Manifest
+++ b/sdk_container/src/third_party/portage-stable/sys-libs/zlib/Manifest
@@ -1 +1,3 @@
+DIST zlib-1.2.11-cygwin-gzopen_w.patch 1170 BLAKE2B fe351436716634bd823da8c2811d332327d335d450d89bee85d7713b09dd454fe6aee264b044a41bf3be603aa36d67943ba6c7d8b46470e180e9b639728b5274 SHA512 14cc63a17fbf6afb6c8a8dd0b92df9807b48e0faf09c88f952083f10716ae62be8de2a0e1424b77fb538605b88898b381160521f2872afdda59e12bd27535c5a
 DIST zlib-1.2.11.tar.gz 607698 BLAKE2B 6bfc4bca5dcadba8a0d4121a2b3ed0bfe440c261003521862c8e6381f1a6f0a72d3fc037351d30afd7ef321e8e8d2ec817c046ac749f2ca0c97fbdc2f7e840b7 SHA512 73fd3fff4adeccd4894084c15ddac89890cd10ef105dd5e1835e1e9bbb6a49ff229713bd197d203edfa17c2727700fce65a2a235f07568212d820dca88b528ae
+DIST zlib-1.2.7-cygwin-minizip.patch 2626 BLAKE2B 885f1fda877c0b783618b163702fb46126b7db572767cd4edb86bd92db1f432c887ef1724e70c8319c26886368dba3a962af5284ec0875c20ec8ad2245fd100a SHA512 e372f1e06311e843eca2092e182c41abb009b5e9880b60292d708e4bc0de5a9e4c43d49b25b0c09df4784bc46a1254472bc5cdbdd8d6c762a9f6a145a555bfe7
diff --git a/sdk_container/src/third_party/portage-stable/sys-libs/zlib/metadata.xml b/sdk_container/src/third_party/portage-stable/sys-libs/zlib/metadata.xml
index 105b205e9e..4d41ee8a0c 100644
--- a/sdk_container/src/third_party/portage-stable/sys-libs/zlib/metadata.xml
+++ b/sdk_container/src/third_party/portage-stable/sys-libs/zlib/metadata.xml
@@ -1,14 +1,15 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
+<!DOCTYPE pkgmetadata SYSTEM "https://www.gentoo.org/dtd/metadata.dtd">
 <pkgmetadata>
-<maintainer type="project">
-	<email>base-system@gentoo.org</email>
-	<name>Gentoo Base System</name>
-</maintainer>
-<use>
-	<flag name="minizip">include the minizip library for quick and dirty zip extraction</flag>
-</use>
-<upstream>
-	<remote-id type="cpe">cpe:/a:gnu:zlib</remote-id>
-</upstream>
+	<maintainer type="project">
+		<email>base-system@gentoo.org</email>
+		<name>Gentoo Base System</name>
+	</maintainer>
+	<use>
+		<flag name="minizip">include the minizip library for quick and dirty zip extraction</flag>
+	</use>
+	<upstream>
+		<remote-id type="github">madler/zlib</remote-id>
+		<remote-id type="cpe">cpe:/a:gnu:zlib</remote-id>
+	</upstream>
 </pkgmetadata>
diff --git a/sdk_container/src/third_party/portage-stable/sys-libs/zlib/zlib-1.2.11-r2.ebuild b/sdk_container/src/third_party/portage-stable/sys-libs/zlib/zlib-1.2.11-r2.ebuild
deleted file mode 100644
index 4b7ac2eecf..0000000000
--- a/sdk_container/src/third_party/portage-stable/sys-libs/zlib/zlib-1.2.11-r2.ebuild
+++ /dev/null
@@ -1,123 +0,0 @@
-# Copyright 1999-2018 Gentoo Foundation
-# Distributed under the terms of the GNU General Public License v2
-
-EAPI="5"
-AUTOTOOLS_AUTO_DEPEND="no"
-
-inherit autotools toolchain-funcs multilib multilib-minimal
-
-DESCRIPTION="Standard (de)compression library"
-HOMEPAGE="https://zlib.net/"
-SRC_URI="https://zlib.net/${P}.tar.gz
-	http://www.gzip.org/zlib/${P}.tar.gz
-	http://www.zlib.net/current/beta/${P}.tar.gz"
-
-LICENSE="ZLIB"
-SLOT="0/1" # subslot = SONAME
-KEYWORDS="alpha amd64 arm arm64 hppa ia64 m68k ~mips ppc ppc64 s390 sh sparc x86 ~amd64-fbsd ~x86-fbsd"
-IUSE="minizip static-libs"
-
-DEPEND="minizip? ( ${AUTOTOOLS_DEPEND} )"
-RDEPEND="!<dev-libs/libxml2-2.7.7" #309623
-
-src_prepare() {
-	epatch "${FILESDIR}"/${PN}-1.2.11-fix-deflateParams-usage.patch
-	epatch "${FILESDIR}"/${PN}-1.2.11-minizip-drop-crypt-header.patch #658536
-
-	if use minizip ; then
-		cd contrib/minizip || die
-		eautoreconf
-	fi
-
-	case ${CHOST} in
-	*-mingw*|mingw*)
-		# uses preconfigured Makefile rather than configure script
-		multilib_copy_sources
-		;;
-	esac
-}
-
-echoit() { echo "$@"; "$@"; }
-
-multilib_src_configure() {
-	case ${CHOST} in
-	*-mingw*|mingw*)
-		;;
-	*)      # not an autoconf script, so can't use econf
-		local uname=$("${EPREFIX}"/usr/share/gnuconfig/config.sub "${CHOST}" | cut -d- -f3) #347167
-		echoit "${S}"/configure \
-			--shared \
-			--prefix="${EPREFIX}/usr" \
-			--libdir="${EPREFIX}/usr/$(get_libdir)" \
-			${uname:+--uname=${uname}} \
-			|| die
-		;;
-	esac
-
-	if use minizip ; then
-		local minizipdir="contrib/minizip"
-		mkdir -p "${BUILD_DIR}/${minizipdir}" || die
-		cd ${minizipdir} || die
-		ECONF_SOURCE="${S}/${minizipdir}" \
-		econf $(use_enable static-libs static)
-	fi
-}
-
-multilib_src_compile() {
-	case ${CHOST} in
-	*-mingw*|mingw*)
-		emake -f win32/Makefile.gcc STRIP=true PREFIX=${CHOST}-
-		sed \
-			-e 's|@prefix@|/usr|g' \
-			-e 's|@exec_prefix@|${prefix}|g' \
-			-e 's|@libdir@|${exec_prefix}/'$(get_libdir)'|g' \
-			-e 's|@sharedlibdir@|${exec_prefix}/'$(get_libdir)'|g' \
-			-e 's|@includedir@|${prefix}/include|g' \
-			-e 's|@VERSION@|'${PV}'|g' \
-			zlib.pc.in > zlib.pc || die
-		;;
-	*)
-		emake
-		;;
-	esac
-	use minizip && emake -C contrib/minizip
-}
-
-sed_macros() {
-	# clean up namespace a little #383179
-	# we do it here so we only have to tweak 2 files
-	sed -i -r 's:\<(O[FN])\>:_Z_\1:g' "$@" || die
-}
-
-multilib_src_install() {
-	case ${CHOST} in
-	*-mingw*|mingw*)
-		emake -f win32/Makefile.gcc install \
-			BINARY_PATH="${ED}/usr/bin" \
-			LIBRARY_PATH="${ED}/usr/$(get_libdir)" \
-			INCLUDE_PATH="${ED}/usr/include" \
-			SHARED_MODE=1
-		# overwrites zlib.pc created from win32/Makefile.gcc #620136
-		insinto /usr/$(get_libdir)/pkgconfig
-		doins zlib.pc
-		;;
-
-	*)
-		emake install DESTDIR="${D}" LDCONFIG=:
-		gen_usr_ldscript -a z
-		;;
-	esac
-	sed_macros "${ED}"/usr/include/*.h
-
-	if use minizip ; then
-		emake -C contrib/minizip install DESTDIR="${D}"
-		sed_macros "${ED}"/usr/include/minizip/*.h
-	fi
-
-	use static-libs || rm -f "${ED}"/usr/$(get_libdir)/lib{z,minizip}.{a,la} #419645
-}
-
-multilib_src_install_all() {
-	dodoc FAQ README ChangeLog doc/*.txt
-	use minizip && dodoc contrib/minizip/*.txt
-}
diff --git a/sdk_container/src/third_party/portage-stable/sys-libs/zlib/zlib-1.2.11-r1.ebuild b/sdk_container/src/third_party/portage-stable/sys-libs/zlib/zlib-1.2.11-r4.ebuild
similarity index 50%
rename from sdk_container/src/third_party/portage-stable/sys-libs/zlib/zlib-1.2.11-r1.ebuild
rename to sdk_container/src/third_party/portage-stable/sys-libs/zlib/zlib-1.2.11-r4.ebuild
index aeddd1a694..bc2fe9834e 100644
--- a/sdk_container/src/third_party/portage-stable/sys-libs/zlib/zlib-1.2.11-r1.ebuild
+++ b/sdk_container/src/third_party/portage-stable/sys-libs/zlib/zlib-1.2.11-r4.ebuild
@@ -1,27 +1,51 @@
-# Copyright 1999-2018 Gentoo Foundation
+# Copyright 1999-2021 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
-EAPI=5
-AUTOTOOLS_AUTO_DEPEND="no"
+EAPI=7
 
-inherit autotools toolchain-funcs multilib multilib-minimal
+AUTOTOOLS_AUTO_DEPEND="no"
+inherit autotools multilib-minimal usr-ldscript
+
+CYGWINPATCHES=(
+	"https://github.com/cygwinports/zlib/raw/22a3462cae33a82ad966ea0a7d6cbe8fc1368fec/1.2.11-gzopen_w.patch -> ${PN}-1.2.11-cygwin-gzopen_w.patch"
+	"https://github.com/cygwinports/zlib/raw/22a3462cae33a82ad966ea0a7d6cbe8fc1368fec/1.2.7-minizip-cygwin.patch -> ${PN}-1.2.7-cygwin-minizip.patch"
+)
 
 DESCRIPTION="Standard (de)compression library"
 HOMEPAGE="https://zlib.net/"
 SRC_URI="https://zlib.net/${P}.tar.gz
 	http://www.gzip.org/zlib/${P}.tar.gz
-	http://www.zlib.net/current/beta/${P}.tar.gz"
+	http://www.zlib.net/current/beta/${P}.tar.gz
+	elibc_Cygwin? ( ${CYGWINPATCHES[*]} )"
 
 LICENSE="ZLIB"
 SLOT="0/1" # subslot = SONAME
-KEYWORDS="alpha amd64 arm arm64 hppa ia64 m68k ~mips ppc ppc64 s390 sh sparc x86 ~amd64-fbsd ~x86-fbsd"
+KEYWORDS="~alpha amd64 arm arm64 hppa ~ia64 ~m68k ~mips ppc ppc64 ~riscv ~s390 sparc x86 ~x64-cygwin ~amd64-linux ~x86-linux ~ppc-macos ~x64-macos ~sparc-solaris ~sparc64-solaris ~x64-solaris ~x86-solaris ~x86-winnt"
 IUSE="minizip static-libs"
 
-DEPEND="minizip? ( ${AUTOTOOLS_DEPEND} )"
-RDEPEND="!<dev-libs/libxml2-2.7.7" #309623
+BDEPEND="minizip? ( ${AUTOTOOLS_DEPEND} )"
+# See #309623 for libxml2
+RDEPEND="
+	!<dev-libs/libxml2-2.7.7
+	!sys-libs/zlib-ng[compat]
+"
+DEPEND="${RDEPEND}"
+
+PATCHES=(
+	"${FILESDIR}"/${PN}-1.2.11-fix-deflateParams-usage.patch
+	"${FILESDIR}"/${PN}-1.2.11-minizip-drop-crypt-header.patch #658536
+)
 
 src_prepare() {
-	epatch "${FILESDIR}"/${PN}-1.2.11-fix-deflateParams-usage.patch
+	default
+
+	if use elibc_Cygwin ; then
+		local p
+		for p in "${CYGWINPATCHES[@]}" ; do
+			# Strip out the "... -> " from the array
+			eapply -p2 "${DISTDIR}/${p#*> }"
+		done
+	fi
 
 	if use minizip ; then
 		cd contrib/minizip || die
@@ -29,7 +53,17 @@ src_prepare() {
 	fi
 
 	case ${CHOST} in
-	*-mingw*|mingw*)
+	*-cygwin*)
+		# do not use _wopen, is a mingw symbol only
+		sed -i -e '/define WIDECHAR/d' "${S}"/gzguts.h || die
+		# zlib1.dll is the mingw name, need cygz.dll
+		# cygz.dll is loaded by toolchain, put into subdir
+		sed -i -e 's|zlib1.dll|win32/cygz.dll|' win32/Makefile.gcc || die
+		;;
+	esac
+
+	case ${CHOST} in
+	*-mingw*|mingw*|*-cygwin*)
 		# uses preconfigured Makefile rather than configure script
 		multilib_copy_sources
 		;;
@@ -40,16 +74,18 @@ echoit() { echo "$@"; "$@"; }
 
 multilib_src_configure() {
 	case ${CHOST} in
-	*-mingw*|mingw*)
+	*-mingw*|mingw*|*-cygwin*)
 		;;
-	*)      # not an autoconf script, so can't use econf
+	*)
 		local uname=$("${EPREFIX}"/usr/share/gnuconfig/config.sub "${CHOST}" | cut -d- -f3) #347167
-		echoit "${S}"/configure \
-			--shared \
-			--prefix="${EPREFIX}/usr" \
-			--libdir="${EPREFIX}/usr/$(get_libdir)" \
-			${uname:+--uname=${uname}} \
-			|| die
+		local myconf=(
+			--shared
+			--prefix="${EPREFIX}/usr"
+			--libdir="${EPREFIX}/usr/$(get_libdir)"
+			${uname:+--uname=${uname}}
+		)
+		# not an autoconf script, so can't use econf
+		echoit "${S}"/configure "${myconf[@]}" || die
 		;;
 	esac
 
@@ -64,10 +100,10 @@ multilib_src_configure() {
 
 multilib_src_compile() {
 	case ${CHOST} in
-	*-mingw*|mingw*)
+	*-mingw*|mingw*|*-cygwin*)
 		emake -f win32/Makefile.gcc STRIP=true PREFIX=${CHOST}-
 		sed \
-			-e 's|@prefix@|/usr|g' \
+			-e 's|@prefix@|'"${EPREFIX}"'/usr|g' \
 			-e 's|@exec_prefix@|${prefix}|g' \
 			-e 's|@libdir@|${exec_prefix}/'$(get_libdir)'|g' \
 			-e 's|@sharedlibdir@|${exec_prefix}/'$(get_libdir)'|g' \
@@ -90,7 +126,7 @@ sed_macros() {
 
 multilib_src_install() {
 	case ${CHOST} in
-	*-mingw*|mingw*)
+	*-mingw*|mingw*|*-cygwin*)
 		emake -f win32/Makefile.gcc install \
 			BINARY_PATH="${ED}/usr/bin" \
 			LIBRARY_PATH="${ED}/usr/$(get_libdir)" \
@@ -113,7 +149,16 @@ multilib_src_install() {
 		sed_macros "${ED}"/usr/include/minizip/*.h
 	fi
 
-	use static-libs || rm -f "${ED}"/usr/$(get_libdir)/lib{z,minizip}.{a,la} #419645
+	if use minizip; then
+		# This might not exist if slibtool is used.
+		# https://bugs.gentoo.org/816756
+		rm -f "${ED}"/usr/$(get_libdir)/libminizip.la || die
+	fi
+
+	if ! use static-libs ; then
+		# https://bugs.gentoo.org/419645
+		rm "${ED}"/usr/$(get_libdir)/libz.a || die
+	fi
 }
 
 multilib_src_install_all() {
diff --git a/sdk_container/src/third_party/portage-stable/sys-libs/zlib/zlib-1.2.11.ebuild b/sdk_container/src/third_party/portage-stable/sys-libs/zlib/zlib-1.2.11.ebuild
deleted file mode 100644
index a7d2cb8d2a..0000000000
--- a/sdk_container/src/third_party/portage-stable/sys-libs/zlib/zlib-1.2.11.ebuild
+++ /dev/null
@@ -1,120 +0,0 @@
-# Copyright 1999-2018 Gentoo Foundation
-# Distributed under the terms of the GNU General Public License v2
-
-EAPI=5
-AUTOTOOLS_AUTO_DEPEND="no"
-
-inherit autotools toolchain-funcs multilib multilib-minimal
-
-DESCRIPTION="Standard (de)compression library"
-HOMEPAGE="https://zlib.net/"
-SRC_URI="https://zlib.net/${P}.tar.gz
-	http://www.gzip.org/zlib/${P}.tar.gz
-	http://www.zlib.net/current/beta/${P}.tar.gz"
-
-LICENSE="ZLIB"
-SLOT="0/1" # subslot = SONAME
-KEYWORDS="alpha amd64 arm arm64 hppa ia64 m68k ~mips ppc ppc64 s390 sh sparc x86 ~amd64-fbsd ~x86-fbsd"
-IUSE="minizip static-libs"
-
-DEPEND="minizip? ( ${AUTOTOOLS_DEPEND} )"
-RDEPEND="!<dev-libs/libxml2-2.7.7" #309623
-
-src_prepare() {
-	if use minizip ; then
-		cd contrib/minizip || die
-		eautoreconf
-	fi
-
-	case ${CHOST} in
-	*-mingw*|mingw*)
-		# uses preconfigured Makefile rather than configure script
-		multilib_copy_sources
-		;;
-	esac
-}
-
-echoit() { echo "$@"; "$@"; }
-
-multilib_src_configure() {
-	case ${CHOST} in
-	*-mingw*|mingw*)
-		;;
-	*)      # not an autoconf script, so can't use econf
-		local uname=$("${EPREFIX}"/usr/share/gnuconfig/config.sub "${CHOST}" | cut -d- -f3) #347167
-		echoit "${S}"/configure \
-			--shared \
-			--prefix="${EPREFIX}/usr" \
-			--libdir="${EPREFIX}/usr/$(get_libdir)" \
-			${uname:+--uname=${uname}} \
-			|| die
-		;;
-	esac
-
-	if use minizip ; then
-		local minizipdir="contrib/minizip"
-		mkdir -p "${BUILD_DIR}/${minizipdir}" || die
-		cd ${minizipdir} || die
-		ECONF_SOURCE="${S}/${minizipdir}" \
-		econf $(use_enable static-libs static)
-	fi
-}
-
-multilib_src_compile() {
-	case ${CHOST} in
-	*-mingw*|mingw*)
-		emake -f win32/Makefile.gcc STRIP=true PREFIX=${CHOST}-
-		sed \
-			-e 's|@prefix@|/usr|g' \
-			-e 's|@exec_prefix@|${prefix}|g' \
-			-e 's|@libdir@|${exec_prefix}/'$(get_libdir)'|g' \
-			-e 's|@sharedlibdir@|${exec_prefix}/'$(get_libdir)'|g' \
-			-e 's|@includedir@|${prefix}/include|g' \
-			-e 's|@VERSION@|'${PV}'|g' \
-			zlib.pc.in > zlib.pc || die
-		;;
-	*)
-		emake
-		;;
-	esac
-	use minizip && emake -C contrib/minizip
-}
-
-sed_macros() {
-	# clean up namespace a little #383179
-	# we do it here so we only have to tweak 2 files
-	sed -i -r 's:\<(O[FN])\>:_Z_\1:g' "$@" || die
-}
-
-multilib_src_install() {
-	case ${CHOST} in
-	*-mingw*|mingw*)
-		emake -f win32/Makefile.gcc install \
-			BINARY_PATH="${ED}/usr/bin" \
-			LIBRARY_PATH="${ED}/usr/$(get_libdir)" \
-			INCLUDE_PATH="${ED}/usr/include" \
-			SHARED_MODE=1
-		# overwrites zlib.pc created from win32/Makefile.gcc #620136
-		insinto /usr/$(get_libdir)/pkgconfig
-		doins zlib.pc
-		;;
-
-	*)
-		emake install DESTDIR="${D}" LDCONFIG=:
-		gen_usr_ldscript -a z
-		;;
-	esac
-	sed_macros "${ED}"/usr/include/*.h
-
-	if use minizip ; then
-		emake -C contrib/minizip install DESTDIR="${D}"
-		sed_macros "${ED}"/usr/include/minizip/*.h
-	fi
-
-	use static-libs || rm -f "${ED}"/usr/$(get_libdir)/lib{z,minizip}.{a,la} #419645
-}
-
-multilib_src_install_all() {
-	dodoc FAQ README ChangeLog doc/*.txt
-	use minizip && dodoc contrib/minizip/*.txt
-}