sys-apps/locale-gen: Add from Gentoo

It's from Gentoo commit 9b2ee03ef894782d6d8d426a8eb8eeb8084ef4fc.

sdk_container/src/third_party/portage-stable/sys-apps/locale-gen/Manifest

@@ -0,0 +1 @@
+DIST locale-gen-2.23.tar.bz2 7664 BLAKE2B a529b62fbb840c9352f06e8f5c80fc764425a2619dc69cc820f550a026d391788d5e2cfeeb46a8b5b9716da63340b4fce57a5b523edd4196ee1219c1200cb752 SHA512 c1245caadb04403c535a836f19bc410d0f04b5c0e297ea5be9852e6d71e08e528071ae769d63d31a677dda8fdd618b4c4d581ed525cf8786b82d8f37636db754

sdk_container/src/third_party/portage-stable/sys-apps/locale-gen/locale-gen-2.23-r1.ebuild

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+# Copyright 2023 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+inherit prefix
+
+DESCRIPTION="Generate locales based upon the config file /etc/locale.gen"
+HOMEPAGE="https://gitweb.gentoo.org/proj/locale-gen.git/"
+SRC_URI="https://gitweb.gentoo.org/proj/locale-gen.git/snapshot/${P}.tar.bz2"
+
+# Totally unclear what the license is. Following here the statement
+# in the Debian file that the tools accompanying glibc are GPL-2+
+LICENSE="GPL-2+"
+
+SLOT="0"
+KEYWORDS="~alpha amd64 arm arm64 hppa ~ia64 ~loong ~m68k ~mips ppc ppc64 ~riscv ~s390 sparc x86"
+
+RDEPEND="
+	app-alternatives/awk
+	app-alternatives/gzip
+	sys-apps/gentoo-functions
+	sys-apps/grep
+	!<sys-libs/glibc-2.37-r3
+"
+DEPEND=""
+
+src_prepare() {
+	default
+	eprefixify locale-gen
+}
+
+src_install() {
+	dosbin locale-gen
+	doman *.[0-8]
+	insinto /etc
+	doins locale.gen
+	keepdir /usr/lib/locale
+}

sdk_container/src/third_party/portage-stable/sys-apps/locale-gen/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>toolchain@gentoo.org</email>
+		<name>Gentoo Toolchain Project</name>
+	</maintainer>
+	<upstream>
+		<remote-id type="gentoo">proj/locale-gen</remote-id>
+		<remote-id type="github">gentoo/locale-gen</remote-id>
+	</upstream>
+</pkgmetadata>