Conditional check for gdesktopappinfo header

GDesktopAppInfo is not available on macOS and needs to be disabled

config.h.meson

@@ -284,3 +284,6 @@
 #mesondefine HAVE_TRACKER3
 
 #mesondefine HAVE_F16C
+
+/* Does the OS support GDesktopAppInfo? */
+#mesondefine HAVE_DESKTOPAPPINFO

gdk/x11/gdkapplaunchcontext-x11.c

@@ -27,7 +27,9 @@
 #include "gdkdisplay-x11.h"
 
 #include <glib.h>
+#ifdef HAVE_DESKTOPAPPINFO
 #include <gio/gdesktopappinfo.h>
+#endif
 
 #include <string.h>
 #include <unistd.h>
@@ -349,10 +351,11 @@ gdk_x11_app_launch_context_get_startup_notify_id (GAppLaunchContext *context,
     workspace_str = g_strdup_printf ("%d", ctx->workspace);
   else
     workspace_str = NULL;
-
+#ifdef HAVE_DESKTOPAPPINFO
   if (G_IS_DESKTOP_APP_INFO (info))
     application_id = g_desktop_app_info_get_filename (G_DESKTOP_APP_INFO (info));
   else
+#endif
     application_id = NULL;
 
   startup_id = g_strdup_printf ("%s-%lu-%s-%s-%d_TIME%lu",

meson.build

@@ -177,6 +177,7 @@ check_headers = [
   'sys/time.h',
   'sys/types.h',
   'unistd.h',
+  'gio/gdesktopappinfo.h'
 ]
 
 foreach h : check_headers