tests: Fix defaultvalue test on macOS

Without these includes, the g_osx_app_info_get_type() in
giotypefuncs.inc is missing a declaration.

gio/tests/defaultvalue.c

@@ -17,9 +17,15 @@
  * along with this library; if not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "config.h"
+
 #include <string.h>
 #include <gio/gio.h>
 
+#ifdef HAVE_COCOA
+#include <gio/gosxappinfo.h>
+#endif
+
 static void
 check_property (const char *output,
 	        GParamSpec *pspec,