eclass/out-of-source: Add from Gentoo

It's from Gentoo commit 2cba2db27919bc449ed2a7bf7ed3259c6b96e65f.

sdk_container/src/third_party/portage-stable/eclass/out-of-source.eclass

@@ -0,0 +1,132 @@
+# Copyright 1999-2023 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+# @ECLASS: out-of-source.eclass
+# @MAINTAINER:
+# Michał Górny <mgorny@gentoo.org>
+# @SUPPORTED_EAPIS: 7 8
+# @BLURB: convenient wrapper to build autotools packages out-of-source
+# @DESCRIPTION:
+# This eclass provides a minimalistic wrapper interface to easily
+# build autotools (and alike) packages out-of-source. It is meant
+# to resemble the interface used by multilib-minimal without actually
+# requiring the package to be multilib.
+#
+# For the simplest ebuilds, it is enough to inherit the eclass
+# and the new phase functions will automatically build the package
+# out-of-source. If you need to redefine one of the default phases
+# src_configure() through src_install(), you need to define
+# the matching sub-phases: my_src_configure(), my_src_compile(),
+# my_src_test() and/or my_src_install(). Those sub-phase functions
+# will be run inside the build directory. Additionally,
+# my_src_install_all() is provided to perform doc-install and other
+# common tasks that are done in source directory.
+#
+# Example use:
+# @CODE
+# inherit out-of-source
+#
+# my_src_configure() {
+#     econf \
+#         --disable-static
+# }
+# @CODE
+
+case ${EAPI} in
+	7|8);;
+	*) die "${ECLASS}: EAPI ${EAPI:-0} not supported" ;;
+esac
+
+if [[ -z ${_OUT_OF_SOURCE_ECLASS} ]]; then
+_OUT_OF_SOURCE_ECLASS=1
+
+# @ECLASS_VARIABLE: BUILD_DIR
+# @OUTPUT_VARIABLE
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# The current build directory.  Defaults to ${WORKDIR}/${P}_build
+# if unset.
+
+# @FUNCTION: out-of-source_src_configure
+# @DESCRIPTION:
+# The default src_configure() implementation establishes a BUILD_DIR,
+# sets ECONF_SOURCE to the current directory (usually S), and runs
+# my_src_configure() (or the default) inside it.
+out-of-source_src_configure() {
+	debug-print-function ${FUNCNAME} "$@"
+
+	# set some BUILD_DIR if we don't have one yet
+	: "${BUILD_DIR:=${WORKDIR}/${P}_build}"
+	local ECONF_SOURCE=${PWD}
+
+	mkdir -p "${BUILD_DIR}" || die
+	pushd "${BUILD_DIR}" >/dev/null || die
+	if declare -f my_src_configure >/dev/null ; then
+		my_src_configure
+	else
+		default_src_configure
+	fi
+	popd >/dev/null || die
+}
+
+# @FUNCTION: out-of-source_src_compile
+# @DESCRIPTION:
+# The default src_compile() implementation runs my_src_compile()
+# (or the default) inside the build directory.
+out-of-source_src_compile() {
+	debug-print-function ${FUNCNAME} "$@"
+
+	pushd "${BUILD_DIR}" >/dev/null || die
+	if declare -f my_src_compile >/dev/null ; then
+		my_src_compile
+	else
+		default_src_compile
+	fi
+	popd >/dev/null || die
+}
+
+# @FUNCTION: out-of-source_src_test
+# @DESCRIPTION:
+# The default src_test() implementation runs my_src_test()
+# (or the default) inside the build directory.
+out-of-source_src_test() {
+	debug-print-function ${FUNCNAME} "$@"
+
+	pushd "${BUILD_DIR}" >/dev/null || die
+	if declare -f my_src_test >/dev/null ; then
+		my_src_test
+	else
+		default_src_test
+	fi
+	popd >/dev/null || die
+}
+
+# @FUNCTION: out-of-source_src_install
+# @DESCRIPTION:
+# The default src_install() implementation runs my_src_install()
+# (or the 'make install' part of the default) inside the build directory,
+# followed by a call to my_src_install_all() (or 'einstalldocs' part
+# of the default) in the original working directory.
+out-of-source_src_install() {
+	debug-print-function ${FUNCNAME} "$@"
+
+	pushd "${BUILD_DIR}" >/dev/null || die
+	if declare -f my_src_install >/dev/null ; then
+		my_src_install
+	else
+		if [[ -f Makefile || -f GNUmakefile || -f makefile ]] ; then
+			emake DESTDIR="${D}" install
+		fi
+	fi
+	popd >/dev/null || die
+
+	if declare -f my_src_install_all >/dev/null ; then
+		my_src_install_all
+	else
+		einstalldocs
+	fi
+}
+
+fi
+
+EXPORT_FUNCTIONS src_configure src_compile src_test src_install