sys-kernel/installkernel-gentoo: Add from gentoo

It's from gentoo commit 38b155fa1bf907617067c98eb4ba3a5d0790eb1a.

sdk_container/src/third_party/portage-stable/sys-kernel/installkernel-gentoo/Manifest

@@ -0,0 +1,3 @@
+DIST installkernel-gentoo-1.tar.gz 2308 BLAKE2B 94d30463445cca4ccea8b00c61dd9f9f89ea4d6f2185e5c1355145300b001fbb624d2e06c9707ecc79ddcab8609725c34239e00b5d80bff22b10a8bc28132916 SHA512 ce33b1958bcec4ed63f812b00471a49ecb88d0149a4e5ebd283b412cc3eafc647477bf84ad21c066ef2602ee06a24ece08fbac85cc815fae91b0bb43d8db8013
+DIST installkernel-gentoo-2.tar.gz 2339 BLAKE2B 0c9999a4688fac9d27774bc30b7529ed01d9598a73283bd508265a9c694921d7a7974d0d9cda2e0c52fe247b7cbce53918c7b3271fdd01beb150097be0905aec SHA512 157e5c525c7eee1aa79027b847eb938700197abad087ec25548f6cfde227720936d1512070549993d6db0bb51dcef1bf00156f2316b415fa00e001ce1828e471
+DIST installkernel-gentoo-3.tar.gz 2340 BLAKE2B fe5b09ce1423be506907ff68aca953fba0c991f1fe94f91bf537b5e38a606f0f2e541758bc627e244b4dbf5960c02d13dff66fe6e4126f9cc8ddf4b0ca5980b1 SHA512 9ae377e95dedd7af2b75a9a4b572e3417e6bea0eb12fc20b837db800d0fea5f97021aac59504074822382579423b2f19a473f6080816ae9b50610a5479488724

sdk_container/src/third_party/portage-stable/sys-kernel/installkernel-gentoo/installkernel-gentoo-1.ebuild

@@ -0,0 +1,25 @@
+# Copyright 2019-2020 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=7
+
+DESCRIPTION="Gentoo fork of installkernel script from debianutils"
+HOMEPAGE="https://github.com/mgorny/installkernel-gentoo"
+SRC_URI="https://github.com/mgorny/installkernel-gentoo/archive/v${PV}.tar.gz
+	-> ${P}.tar.gz"
+
+LICENSE="GPL-2+"
+SLOT="0"
+KEYWORDS="~alpha ~amd64 ~arm ~arm64 ~hppa ~ia64 ~m68k ~mips ~ppc ~ppc64 ~riscv ~s390 ~sparc ~x86 ~x86-linux"
+
+RDEPEND="
+	>=sys-apps/debianutils-4.9-r1
+	!<sys-apps/debianutils-4.9-r1[installkernel(+)]
+	!sys-kernel/installkernel-systemd-boot"
+
+src_install() {
+	into /
+	dosbin installkernel
+	doman installkernel.8
+	keepdir /etc/kernel/postinst.d
+}

sdk_container/src/third_party/portage-stable/sys-kernel/installkernel-gentoo/installkernel-gentoo-2.ebuild

@@ -0,0 +1,33 @@
+# Copyright 2019-2021 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=7
+
+DESCRIPTION="Gentoo fork of installkernel script from debianutils"
+HOMEPAGE="https://github.com/mgorny/installkernel-gentoo"
+SRC_URI="https://github.com/mgorny/installkernel-gentoo/archive/v${PV}.tar.gz
+	-> ${P}.tar.gz"
+
+LICENSE="GPL-2+"
+SLOT="0"
+KEYWORDS="~alpha amd64 arm arm64 hppa ~ia64 ~m68k ~mips ppc ppc64 ~riscv ~s390 sparc x86 ~x86-linux"
+
+RDEPEND="
+	>=sys-apps/debianutils-4.9-r1
+	!<sys-apps/debianutils-4.9-r1[installkernel(+)]
+	!sys-kernel/installkernel-systemd-boot"
+
+src_install() {
+	into /
+	dosbin installkernel
+	doman installkernel.8
+	keepdir /etc/kernel/postinst.d
+}
+
+pkg_postinst() {
+	if has 1 ${REPLACING_VERSIONS}; then
+		ewarn "In v2, the initramfs filename has changed to initramfs*.img, to match"
+		ewarn "the default names used by dracut and genkernel-4.  If your bootloader"
+		ewarn "config uses the verbatim filename, please update it."
+	fi
+}

sdk_container/src/third_party/portage-stable/sys-kernel/installkernel-gentoo/installkernel-gentoo-3.ebuild

@@ -0,0 +1,33 @@
+# Copyright 2019-2021 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=7
+
+DESCRIPTION="Gentoo fork of installkernel script from debianutils"
+HOMEPAGE="https://github.com/mgorny/installkernel-gentoo"
+SRC_URI="https://github.com/mgorny/installkernel-gentoo/archive/v${PV}.tar.gz
+	-> ${P}.tar.gz"
+
+LICENSE="GPL-2+"
+SLOT="0"
+KEYWORDS="~alpha amd64 arm arm64 hppa ~ia64 ~m68k ~mips ppc ppc64 ~riscv ~s390 sparc x86 ~x86-linux"
+
+RDEPEND="
+	>=sys-apps/debianutils-4.9-r1
+	!<sys-apps/debianutils-4.9-r1[installkernel(+)]
+	!sys-kernel/installkernel-systemd-boot"
+
+src_install() {
+	into /
+	dosbin installkernel
+	doman installkernel.8
+	keepdir /etc/kernel/postinst.d
+}
+
+pkg_postinst() {
+	if has 1 ${REPLACING_VERSIONS}; then
+		ewarn "In v2, the initramfs filename has changed to initramfs*.img, to match"
+		ewarn "the default names used by dracut and genkernel-4.  If your bootloader"
+		ewarn "config uses the verbatim filename, please update it."
+	fi
+}

sdk_container/src/third_party/portage-stable/sys-kernel/installkernel-gentoo/metadata.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE pkgmetadata SYSTEM "https://www.gentoo.org/dtd/metadata.dtd">
+<pkgmetadata>
+	<maintainer type="project">
+		<email>dist-kernel@gentoo.org</email>
+		<name>Distribution Kernel Project</name>
+	</maintainer>
+</pkgmetadata>