eclass/toolchain: Sync with Gentoo

It's from Gentoo commit 5e3d413c90ed50a6f9582ee1e3817398d4a82319.

sdk_container/src/third_party/portage-stable/eclass/toolchain.eclass

@@ -1,4 +1,4 @@
-# Copyright 1999-2023 Gentoo Authors
+# Copyright 1999-2024 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 # @ECLASS: toolchain.eclass
@@ -231,7 +231,7 @@ tc_has_feature() {
 }
 
 if [[ ${PN} != kgcc64 && ${PN} != gcc-* ]] ; then
-	IUSE+=" debug +cxx +nptl" TC_FEATURES+=( nptl )
+	IUSE+=" debug +cxx"
 	IUSE+=" +fortran" TC_FEATURES+=( fortran )
 	IUSE+=" doc hardened multilib objc"
 	IUSE+=" pgo"
@@ -253,8 +253,7 @@ if [[ ${PN} != kgcc64 && ${PN} != gcc-* ]] ; then
 	IUSE+=" ada"
 	IUSE+=" vtv"
 	IUSE+=" jit"
-	tc_version_is_between 5.0 9 && IUSE+=" mpx"
-	IUSE+=" +pie +ssp +pch"
+	IUSE+=" +pie +ssp pch"
 
 	IUSE+=" systemtap" TC_FEATURES+=( systemtap )
 
@@ -303,7 +302,7 @@ if tc_has_feature graphite ; then
 fi
 
 BDEPEND="
-	>=sys-devel/bison-1.875
+	app-alternatives/yacc
 	>=sys-devel/flex-2.5.4
 	nls? ( sys-devel/gettext )
 	test? (
@@ -338,7 +337,7 @@ if tc_has_feature zstd ; then
 fi
 
 if tc_has_feature valgrind ; then
-	BDEPEND+=" valgrind? ( dev-util/valgrind )"
+	BDEPEND+=" valgrind? ( dev-debug/valgrind )"
 fi
 
 # TODO: Add a pkg_setup & pkg_pretend check for whether the active compiler
@@ -1239,14 +1238,6 @@ toolchain_src_configure() {
 		confgcc+=( $(use_enable cet) )
 	fi
 
-	if in_iuse cilk ; then
-		confgcc+=( $(use_enable cilk libcilkrts) )
-	fi
-
-	if in_iuse mpx ; then
-		confgcc+=( $(use_enable mpx libmpx) )
-	fi
-
 	if in_iuse systemtap ; then
 		confgcc+=( $(use_enable systemtap) )
 	fi
@@ -2002,8 +1993,6 @@ toolchain_src_install() {
 	# libgfortran.la: gfortran itself handles linkage correctly in the
 	# dynamic & static case (libgfortran.spec). bug #573302
 	# libgfortranbegin.la: Same as above, and it's an internal lib.
-	# libmpx.la: gcc itself handles linkage correctly (libmpx.spec).
-	# libmpxwrappers.la: See above.
 	# libitm.la: gcc itself handles linkage correctly (libitm.spec).
 	# libvtv.la: gcc itself handles linkage correctly.
 	# lib*san.la: Sanitizer linkage is handled internally by gcc, and they
@@ -2020,8 +2009,6 @@ toolchain_src_install() {
 			-name 'libgomp-plugin-*.la' -o \
 			-name libgfortran.la -o \
 			-name libgfortranbegin.la -o \
-			-name libmpx.la -o \
-			-name libmpxwrappers.la -o \
 			-name libitm.la -o \
 			-name libvtv.la -o \
 			-name 'lib*san.la' \