Exit with a better error code

OBS-URL: https://build.opensuse.org/package/show/openSUSE:Factory/appstream-glib?expand=0&rev=50

openSUSE-appstream-process

@@ -19,9 +19,11 @@ TMPDIR=$(mktemp -d)
   --packages-dir=${SRC}					\
   --output-dir=${DEST}
 
-if [ $? -ne 0 ]; then
+RET=$?
+
+if [ $RET -ne 0 ]; then
   # The appstream-builder failed, exit with an error code, so prod builder knows about it
-  exit 1
+  exit $RET
 fi
 
 # clean up TMPDIR again