Teach ninja to handle output directories outside the source dir.

test/generator-output/gyptest-subdir2-deep.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 building a target from a .gyp file a few subdirectories
 deep when the --generator-output= option is used to put the build
 configuration files in a separate directory tree.
 """
 
 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('src'), False)
 
 test.writable(test.workpath('src/subdir2/deeper/build'), True)
 
 test.run_gyp('deeper.gyp',
              '-Dset_symroot=1',
              '--generator-output=' + test.workpath('gypfiles'),
              chdir='src/subdir2/deeper')
 
 test.build('deeper.gyp', test.ALL, chdir='gypfiles')
 
 chdir = 'gypfiles'
 
 if test.format == 'xcode':
   chdir = 'src/subdir2/deeper'
 test.run_built_executable('deeper',
                           chdir=chdir,
                           stdout="Hello from deeper.c\n")
 
 test.pass_test()