Specify dependences correctly when building mac tools for iOS.

build/ios/mac_build.gypi

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Xcode throws an error if an iOS target depends on a Mac OS X target. So
 # any place a utility program needs to be build and run, an action is
 # used to run ninja as script to work around this.
 # Example:
 # {
 #   'target_name': 'foo',
 #   'type': 'none',
 #   'variables': {
 #     # The name of a directory used for ninja. This cannot be shared with
 #     # another mac build.
 #     'ninja_output_dir': 'ninja-foo',
+#     # The full path to the location in which the ninja executable should be
+#     # placed. This cannot be shared with another mac build.
+#    'ninja_product_dir':
+#      '<(DEPTH)/xcodebuild/<(ninja_output_dir)/<(CONFIGURATION_NAME)',
 #     # The list of all the gyp files that contain the targets to run.
 #     're_run_targets': [
 #       'foo.gyp',
 #     ],
 #   },
 #   'includes': ['path_to/mac_build.gypi'],
 #   'actions': [
 #     {
 #       'action_name': 'compile foo',
 #       'inputs': [],
 #       'outputs': [],
 #       'action': [
 #         '<@(ninja_cmd)',
 #         # All the targets to build.
 #         'foo1',
 #         'foo2',
 #       ],
 #     },
 #   ],
 # }
 {
   'variables': {
-    # Convenience variable pointing to the ninja product directory.
-    'ninja_product_dir':
-      '<(DEPTH)/xcodebuild/<(ninja_output_dir)/<(CONFIGURATION_NAME)',
-
     # Common ninja command line flags.
     'ninja_cmd': [
       # Bounce through clean_env to clean up the environment so things
       # set by the iOS build don't pollute the Mac build.
       '<(DEPTH)/build/ios/clean_env.py',
       # ninja must be found in the PATH.
       'ADD_TO_PATH=<!(echo $PATH)',
       'ninja',
       '-C',
       '<(ninja_product_dir)',
@@ skipping 18 matching lines @@
 
     # Rerun gyp for each of the projects needed. This is what actually
     # generates the projects on disk.
     're_run_gyp_execution':
       '<!(cd <(DEPTH) && <@(re_run_gyp) <@(re_run_targets))',
   },
   # Since these are used to generate things needed by other targets, make
   # them hard dependencies so they are always built first.
   'hard_dependency': 1,
 }