weston-init: Don't change XDG_RUNTIME_DIR if it already exists

In the case that XDG_RUNTIME_DIR already exists, the mkdir --parents
at least does nothing, but the chmod could overwrite the desired
file mode settings.

(From OE-Core rev: 9f539d03138817b7b740ed1895000704e4a475d0)

Signed-off-by: Tom Hochstein <tom.hochstein@nxp.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-graphics/wayland/weston-init/weston-start

@@ -65,8 +65,10 @@ fi
 
 if test -z "$XDG_RUNTIME_DIR"; then
     export XDG_RUNTIME_DIR=/run/user/`id -u`
-    mkdir --parents $XDG_RUNTIME_DIR
-    chmod 0700 $XDG_RUNTIME_DIR
+    if ! test -d "$XDG_RUNTIME_DIR"; then
+        mkdir --parents $XDG_RUNTIME_DIR
+        chmod 0700 $XDG_RUNTIME_DIR
+    fi
 fi
 
 exec openvt $openvt_args -- $launcher $weston_args --log=@LOCALSTATEDIR@/log/weston.log