tests/date: force English locale running the GDateTime tests

The parsing test needs to make some assumption about the locale
representation of the string to be parsed, so we need to explicitly
override the locale here.

glib/tests/date.c

@@ -351,6 +351,7 @@ main (int argc, char** argv)
     3000, 3001, 3002, 3998, 3999, 4000, 4001, 4002, 4003
   };
 
+  g_setenv ("LANG", "en_US.utf-8", TRUE);
   setlocale (LC_ALL, "");
 
   g_test_init (&argc, &argv, NULL);