Teach ninja to handle output directories outside the source dir.

test/generator-output/gyptest-rules.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 --generator-output= behavior when using rules.
 """
 
 import TestGyp
 
-# Ninja and Android don't support --generator-output.
-test = TestGyp.TestGyp(formats=['!ninja', '!android'])
+# Android doesn't support --generator-output.
+test = TestGyp.TestGyp(formats=['!android'])
 
 test.writable(test.workpath('rules'), False)
 
 test.run_gyp('rules.gyp',
              '--generator-output=' + test.workpath('gypfiles'),
              chdir='rules')
 
 test.writable(test.workpath('rules'), True)
 
 test.relocate('rules', 'relocate/rules')
@@ skipping 25 matching lines @@
 test.must_match('relocate/rules/subdir2/rules-out/file1.out',
                 "Hello from file1.in0\n")
 test.must_match('relocate/rules/subdir2/rules-out/file2.out',
                 "Hello from file2.in0\n")
 test.must_match('relocate/rules/subdir2/rules-out/file3.out',
                 "Hello from file3.in1\n")
 test.must_match('relocate/rules/subdir2/rules-out/file4.out',
                 "Hello from file4.in1\n")
 
 test.pass_test()