qmake-utils.eclass: add qt6 support

Signed-off-by: Thomas Bettler <thomas.bettler@gmail.com>
Closes: https://github.com/gentoo/gentoo/pull/31254
Signed-off-by: Andreas Sturmlechner <asturm@gentoo.org>

eclass/qmake-utils.eclass

@@ -155,4 +155,63 @@ qt6_get_plugindir() {
 	echo $(qt6_get_libdir)/qt6/plugins
 }
 
+# @FUNCTION: qt6_get_qmake_args
+# @DESCRIPTION:
+# Echoes a multi-line string containing arguments to pass to qmake.
+qt6_get_qmake_args() {
+	cat <<-EOF
+		QMAKE_AR="$(tc-getAR) cqs"
+		QMAKE_CC="$(tc-getCC)"
+		QMAKE_LINK_C="$(tc-getCC)"
+		QMAKE_LINK_C_SHLIB="$(tc-getCC)"
+		QMAKE_CXX="$(tc-getCXX)"
+		QMAKE_LINK="$(tc-getCXX)"
+		QMAKE_LINK_SHLIB="$(tc-getCXX)"
+		QMAKE_OBJCOPY="$(tc-getOBJCOPY)"
+		QMAKE_RANLIB=
+		QMAKE_STRIP=
+		QMAKE_CFLAGS="${CFLAGS}"
+		QMAKE_CFLAGS_RELEASE=
+		QMAKE_CFLAGS_DEBUG=
+		QMAKE_CFLAGS_RELEASE_WITH_DEBUGINFO=
+		QMAKE_CXXFLAGS="${CXXFLAGS}"
+		QMAKE_CXXFLAGS_RELEASE=
+		QMAKE_CXXFLAGS_DEBUG=
+		QMAKE_CXXFLAGS_RELEASE_WITH_DEBUGINFO=
+		QMAKE_LFLAGS="${LDFLAGS}"
+		QMAKE_LFLAGS_RELEASE=
+		QMAKE_LFLAGS_DEBUG=
+		QMAKE_LFLAGS_RELEASE_WITH_DEBUGINFO=
+	EOF
+}
+
+# @FUNCTION: eqmake6
+# @USAGE: [arguments for qmake]
+# @DESCRIPTION:
+# Wrapper for Qt6's qmake. All arguments are passed to qmake.
+#
+# For recursive build systems, i.e. those based on the subdirs template,
+# you should run eqmake6 on the top-level project file only, unless you
+# have a valid reason to do otherwise. During the building, qmake will
+# be automatically re-invoked with the right arguments on every directory
+# specified inside the top-level project file.
+eqmake6() {
+	debug-print-function ${FUNCNAME} "$@"
+
+	ebegin "Running qmake"
+
+	local -a args
+	mapfile -t args <<<"$(qt6_get_qmake_args)"
+	# NB: we're passing literal quotes in but qmake doesn't seem to mind
+	"$(qt6_get_bindir)"/qmake -makefile "${args[@]}" "$@"
+
+	if ! eend $? ; then
+		echo
+		eerror "Running qmake has failed! (see above for details)"
+		eerror "This shouldn't happen - please send a bug report to https://bugs.gentoo.org/"
+		echo
+		die "eqmake6 failed"
+	fi
+}
+
 fi