add a rundir for root

Signed-off-by: fbt <fbt@fleshless.org>

rc.in

@@ -185,6 +185,8 @@ rc.main() {
 
 	# Default XDG_RUNTIME_DIR for all non-system users
 	# rtkit:x:133:133:RealtimeKit:/proc:/sbin/nologin
+	# Also add one for root
+	cfg_tmpdirs+=( "/run/user/0:700:0:0" )
 	while IFS=':' read -r _ _ uid gid _; do
 		if (( uid >= 1000 )); then
 			cfg_tmpdirs+=( "/run/user/$uid:700:$uid:$gid" )