weston-launch: Set all groups for user

Signed-off-by: Quentin Glidic <sardemff7+git@sardemff7.net>

https://bugs.freedesktop.org/show_bug.cgi?id=65933
diff --git a/src/weston-launch.c b/src/weston-launch.c
index 76dcede..7d7b556 100644
--- a/src/weston-launch.c
+++ b/src/weston-launch.c
@@ -631,9 +631,13 @@
 		}
 
 		if (setgid(wl.pw->pw_gid) < 0 ||
+#ifdef HAVE_INITGROUPS
+                    initgroups(wl.pw->pw_name, wl.pw->pw_gid) < 0 ||
+#endif
 		    setuid(wl.pw->pw_uid) < 0)
 			error(1, errno, "dropping privilidges failed");
 
+
 		if (sleep_fork) {
 			if (wl.verbose)
 				printf("weston-launch: waiting %d seconds\n", sleep_fork);