glocalfile: Add test case for g_file_trash

g_local_file_trash has been changed to return G_IO_ERROR_NOT_SUPPORTED
for locations on system-internal mounts. Let's verify that.

https://gitlab.gnome.org/GNOME/glib/issues/251

gio/tests/meson.build

@@ -123,6 +123,7 @@ if host_machine.system() != 'windows'
     'unix-streams',
     'g-file-info-filesystem-readonly',
     'gschema-compile',
+    'trash',
   ]
 
   # Uninstalled because of the check-for-executable logic in DesktopAppInfo