[repare-build-dir] Check for unknown meson options

Meson does only emit a warning if unknown options are passed. In our
case, this is always something we should take care of, because an
option we assumed we configured, had no effect.

See also https://github.com/mesonbuild/meson/pull/8658

tools/prepare-build-dir

@@ -14,11 +14,13 @@ cd "`dirname "${SCRIPTDIR}"`" > /dev/null
 SCRIPTDIR="`pwd`";
 popd  > /dev/null
 
+DEBUG=false
 QUIET=false
 while getopts :dq OPT; do
 	case $OPT in
 		d)
 			set -x
+			DEBUG=true
 			;;
 		q)
 			QUIET=true
@@ -87,9 +89,27 @@ for var in $(compgen -e); do
 	MESON_ARGS+=("-D${MESON_BUILD_OPTION_NAME}=${MESON_BUILD_OPTION_VALUE}")
 done
 
+LOGFILE=$(mktemp --tmpdir=/var/tmp)
+cleanup() {
+	rm -f "${LOGFILE}"
+}
+trap cleanup EXIT
+
 if ! $QUIET; then
 	set -x
 fi
-exec meson --buildtype=${BUILDTYPE} \
+
+meson --buildtype=${BUILDTYPE} \
 	 ${MESON_ARGS[@]} \
-	 "${ABSOLUTE_BUILDDIR}"
+	 "${ABSOLUTE_BUILDDIR}" |\
+	tee "${LOGFILE}"
+
+if ! $DEBUG; then
+	set +x
+fi
+
+if grep -F "WARNING: Unknown options:" "${LOGFILE}"; then
+	echo "ERROR: Unknown meson options found"
+	rm -r "${ABSOLUTE_BUILDDIR}" "${ABSOLUTE_BUILDDIR_SYMLINK}"
+	exit 1
+fi