eclass/sgml-catalog-r1: Add from gentoo

It's from gentoo commit 8729279eb1e48f171f86e484610a1fbbd904d67d.

sdk_container/src/third_party/portage-stable/eclass/sgml-catalog-r1.eclass

@@ -0,0 +1,76 @@
+# Copyright 2019 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+# @ECLASS: sgml-catalog-r1.eclass
+# @MAINTAINER:
+# Michał Górny <mgorny@gentoo.org>
+# @AUTHOR:
+# Michał Górny <mgorny@gentoo.org>
+# @SUPPORTED_EAPIS: 7
+# @BLURB: Functions for installing SGML catalogs
+# @DESCRIPTION:
+# This eclass regenerates /etc/sgml/catalog, /etc/sgml.{,c}env
+# and /etc/env.d/93sgmltools-lite as necessary for the DocBook tooling.
+# This is done via exported pkg_postinst and pkg_postrm phases.
+
+case ${EAPI:-0} in
+	7) ;;
+	*) die "Unsupported EAPI=${EAPI} for ${ECLASS}";;
+esac
+
+EXPORT_FUNCTIONS pkg_postinst pkg_postrm
+
+if [[ ! ${_SGML_CATALOG_R1} ]]; then
+
+if [[ ${CATEGORY}/${PN} != app-text/sgml-common ]]; then
+	RDEPEND=">=app-text/sgml-common-0.6.3-r7"
+fi
+
+# @FUNCTION: sgml-catalog-r1_update_catalog
+# @DESCRIPTION:
+# Regenerate /etc/sgml/catalog to include all installed catalogs.
+sgml-catalog-r1_update_catalog() {
+	local shopt_save=$(shopt -p nullglob)
+	shopt -s nullglob
+	local cats=( "${EROOT}"/etc/sgml/*.cat )
+	${shopt_save}
+
+	if [[ ${#cats[@]} -gt 0 ]]; then
+		ebegin "Updating ${EROOT}/etc/sgml/catalog"
+		printf 'CATALOG "%s"\n' "${cats[@]}" > "${T}"/catalog &&
+		mv "${T}"/catalog "${EROOT}"/etc/sgml/catalog
+		eend "${?}"
+	else
+		ebegin "Removing ${EROOT}/etc/sgml/catalog"
+		rm "${EROOT}"/etc/sgml/catalog &&
+		{ rmdir "${EROOT}"/etc/sgml &>/dev/null || :; }
+		eend "${?}"
+	fi
+}
+
+# @FUNCTION: sgml-catalog-r1_update_env
+# @DESCRIPTION:
+# Regenerate environment variables and copy them to env.d.
+sgml-catalog-r1_update_env() {
+	# gensgmlenv doesn't support overriding root
+	if [[ -z ${ROOT} && -x "${EPREFIX}/usr/bin/gensgmlenv" ]]; then
+		ebegin "Regenerating SGML environment variables"
+		gensgmlenv &&
+		grep -v export "${EPREFIX}/etc/sgml/sgml.env" > "${T}"/93sgmltools-lite &&
+		mv "${T}"/93sgmltools-lite "${EPREFIX}/etc/env.d/93sgmltools-lite"
+		eend "${?}"
+	fi
+}
+
+sgml-catalog-r1_pkg_postinst() {
+	sgml-catalog-r1_update_catalog
+	sgml-catalog-r1_update_env
+}
+
+sgml-catalog-r1_pkg_postrm() {
+	sgml-catalog-r1_update_catalog
+	sgml-catalog-r1_update_env
+}
+
+_SGML_CATALOG_R1=1
+fi