[mutter/bilelmoussaoui/sn] startup/x11: Fix compiling without startup-notification

[Bilal Elmoussaoui <bilelmoussaoui src gnome org>]

commit b906465bdf5269d574d6f2258a0697be4a39eae0
Author: Bilal Elmoussaoui <bil elmoussaoui gmail com>
Date:   Wed May 18 21:34:13 2022 +0000

    startup/x11: Fix compiling without startup-notification
    
    If startup_notification is disabled, linking against sn would fail

 src/x11/meta-startup-notification-x11.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/src/x11/meta-startup-notification-x11.c b/src/x11/meta-startup-notification-x11.c
index 42be6d580f..b870f071f2 100644
--- a/src/x11/meta-startup-notification-x11.c
+++ b/src/x11/meta-startup-notification-x11.c
@@ -20,7 +20,6 @@
 #include "meta-startup-notification-x11.h"
 
 #include <gio/gdesktopappinfo.h>
-#include <libsn/sn.h>
 
 #include "core/display-private.h"
 #include "core/startup-notification-private.h"
@@ -29,6 +28,8 @@
 
 #ifdef HAVE_STARTUP_NOTIFICATION
 
+#include <libsn/sn.h>
+
 enum
 {
   PROP_SEQ_X11_0,