Add TestGypXcodeNinja to run tests against the xcode-ninja generator

test/mac/gyptest-app-error.py

 #!/usr/bin/env python
 
 # Copyright (c) 2012 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """
 Verifies that invalid strings files cause the build to fail.
 """
 
@@ skipping 16 matching lines @@
       saw_expected_error[0] = True
       return True
     return False
   test = TestGyp.TestGyp(formats=['ninja', 'make', 'xcode'], match=match)
 
   test.run_gyp('test-error.gyp', chdir='app-bundle')
 
   test.build('test-error.gyp', test.ALL, chdir='app-bundle')
 
   # Ninja pipes stderr of subprocesses to stdout.
-  if test.format == 'ninja' and expected_error in test.stdout():
+  if test.format in ['ninja', 'xcode-ninja'] \
+      and expected_error in test.stdout():
     saw_expected_error[0] = True
 
   if saw_expected_error[0]:
     test.pass_test()
   else:
     test.fail_test()