eclass/strip-linguas: Add from gentoo

It's from gentoo commit 48651ecc0d4444536ed15b06736e331238b6f92b.

sdk_container/src/third_party/portage-stable/eclass/strip-linguas.eclass

@@ -0,0 +1,67 @@
+# Copyright 2004-2021 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+# @ECLASS: strip-linguas.eclass
+# @MAINTAINER:
+# Ulrich Müller <ulm@gentoo.org>
+# @AUTHOR:
+# Mike Frysinger <vapier@gentoo.org>
+# @SUPPORTED_EAPIS: 5 6 7 8
+# @BLURB: convenience function for LINGUAS support
+
+case ${EAPI} in
+	5|6|7|8) ;;
+	*) die "${ECLASS}: EAPI ${EAPI:-0} not supported" ;;
+esac
+
+if [[ -z ${_STRIP_LINGUAS_ECLASS} ]]; then
+_STRIP_LINGUAS_ECLASS=1
+
+# @FUNCTION: strip-linguas
+# @USAGE: [<allow LINGUAS>|<-i|-u> <directories of .po files>]
+# @DESCRIPTION:
+# Make sure that LINGUAS only contains languages that a package can
+# support.  The first form allows you to specify a list of LINGUAS.
+# The -i builds a list of po files found in all the directories and uses
+# the intersection of the lists.  The -u builds a list of po files found
+# in all the directories and uses the union of the lists.
+strip-linguas() {
+	local d f ls newls nols
+
+	if [[ $1 == "-i" ]] || [[ $1 == "-u" ]]; then
+		local op=$1; shift
+		ls=$(find "$1" -name '*.po' -exec basename {} .po ';'); shift
+		for d; do
+			if [[ ${op} == "-u" ]]; then
+				newls=${ls}
+			else
+				newls=""
+			fi
+			for f in $(find "${d}" -name '*.po' -exec basename {} .po ';'); do
+				if [[ ${op} == "-i" ]]; then
+					has ${f} ${ls} && newls+=" ${f}"
+				else
+					has ${f} ${ls} || newls+=" ${f}"
+				fi
+			done
+			ls=${newls}
+		done
+	else
+		ls="$@"
+	fi
+
+	nols=""
+	newls=""
+	for f in ${LINGUAS}; do
+		if has ${f} ${ls}; then
+			newls+=" ${f}"
+		else
+			nols+=" ${f}"
+		fi
+	done
+	[[ -n ${nols} ]] \
+		&& einfo "Sorry, but ${PN} does not support the LINGUAS:" ${nols}
+	export LINGUAS=${newls:1}
+}
+
+fi