quartz: gtk-application - inhibit openFiles events from cmdline

When an application is started via cmdline, then openFiles events
from MacOS are generated although gtkapplication already interprets
the cmdline arguments and opens suitable arguments as files. So they
would be opened twice. Depending on the exact situation the
openFiles event can also be issued before the startup signal
is given. Depending on the application this can result in a crash
due to unexpected behaviour. I took this idea from the
gedit-app-osx.m file. Also from Jesse van den Kieboom.

See:
https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/2098#note_842975
https://gitlab.gnome.org/GNOME/gtk/-/commit/a3ad7fa80f764fb7bcbe
https://gitlab.gnome.org/GNOME/gedit/-/blob/master/gedit/gedit-app-osx.m#L592

gtk/gtkapplication-quartz.c

@@ -337,6 +337,13 @@ gtk_application_impl_quartz_is_inhibited (GtkApplicationImpl         *impl,
 static void
 gtk_application_impl_quartz_init (GtkApplicationImplQuartz *quartz)
 {
+  /* This is required so that Cocoa is not going to parse the
+     command line arguments by itself and generate OpenFile events.
+     We already parse the command line ourselves, so this is needed
+     to prevent opening files twice, etc. */
+  [[NSUserDefaults standardUserDefaults] setObject:@"NO"
+                                            forKey:@"NSTreatUnknownArgumentsAsOpen"];
+
   quartz->combined = g_menu_new ();
 }