eclass/dot-a: Add from Gentoo

It's from Gentoo commit fa1b0ff46e9a6039cf6d205b22250ca72ae5ab56.

sdk_container/src/third_party/portage-stable/eclass/dot-a.eclass

@@ -0,0 +1,119 @@
+# Copyright 2025 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+# @ECLASS: dot-a.eclass
+# @MAINTAINER:
+# Toolchain Ninjas <toolchain@gentoo.org>
+# @AUTHOR:
+# Sam James <sam@gentoo.org>
+# Eli Schwartz <eschwartz@gentoo.org>
+# @SUPPORTED_EAPIS: 8
+# @BLURB: Functions to handle stripping LTO bytecode out of static archives.
+# @DESCRIPTION:
+# This eclass provides functions to strip LTO bytecode out of static archives
+# (.a files).
+#
+# Static libraries when built with LTO will contain LTO bytecode which is
+# not portable across compiler versions or compiler vendors. To avoid pessimising
+# the library and always filtering LTO, we can build it with -ffat-lto-objects
+# instead, which builds some components twice. The installed part will then
+# have the LTO contents stripped out, leaving the regular objects in the
+# static archive.
+#
+# Use should be passing calling lto-guarantee-fat before configure-time
+# and calling strip-lto-bytecode after installation.
+#
+# Most packages installing static libraries should be using this eclass,
+# though it's not strictly necessary if the package filters LTO.
+#
+# @EXAMPLE:
+# @CODE
+#
+# inherit dot-a
+#
+# src_configure() {
+#     lto-guarantee-fat
+#     econf
+# }
+#
+# src_install() {
+#     default
+#     strip-lto-bytecode
+# }
+case ${EAPI} in
+	8) ;;
+	*) die "${ECLASS}: EAPI ${EAPI:-0} not supported" ;;
+esac
+
+if [[ -z ${_DOT_A_ECLASS} ]] ; then
+_DOT_A_ECLASS=1
+
+inherit flag-o-matic toolchain-funcs
+
+# TODO: QA check
+
+# @FUNCTION: lto-guarantee-fat
+# @DESCRIPTION:
+# If LTO is enabled, appends -ffat-lto-objects or any other flags needed
+# to provide fat LTO objects.
+lto-guarantee-fat() {
+	tc-is-lto || return
+
+	# We add this for all languages as LTO obviously can't be done
+	# if different compilers are used for e.g. C vs C++ anyway.
+	append-flags $(test-flags-CC -ffat-lto-objects)
+}
+
+# @FUNCTION: strip-lto-bytecode
+# @USAGE: [library|directory] [...]
+# @DESCRIPTION:
+# Strips LTO bytecode from libraries (static archives) passed as arguments.
+# Defaults to operating on ${ED} as a whole if no arguments are passed.
+#
+# As an optimisation, if USE=static-libs exists for a package and is disabled,
+# the default-searching behaviour with no arguments is suppressed.
+strip-lto-bytecode() {
+	tc-is-lto || return
+
+	local files=()
+
+	if [[ ${#} -eq 0 ]]; then
+		if ! in_iuse static-libs || use static-libs ; then
+			# maybe we are USE=static-libs. Alternatively, maybe the ebuild doesn't
+			# offer such a choice. In both cases, the user specified the function,
+			# so we expect to be called on *something*, but nothing was explicitly
+			# passed. Try scanning ${ED} automatically.
+			set -- "${ED}"
+		else
+			return
+		fi
+	fi
+
+	mapfile -t -d '' files < <(find -H "${@}" -type f \( -name '*.a' -or -name '*.o' \) -print0)
+
+	toolchain_type=
+	tc-is-gcc && toolchain_type=gnu
+	tc-is-clang && toolchain_type=llvm
+
+	local file
+	for file in "${files[@]}" ; do
+		case ${toolchain_type} in
+			gnu)
+				$(tc-getSTRIP) \
+					-R .gnu.lto_* \
+					-R .gnu.debuglto_* \
+					-N __gnu_lto_v1 \
+					"${file}" || die "Stripping bytecode in ${file} failed"
+				;;
+			llvm)
+				llvm-bitcode-strip \
+					-r "${file}" \
+					-o "${file}" || die "Stripping bytecode in ${file} failed"
+				;;
+			*)
+				;;
+		esac
+	done
+}
+
+fi