Rework build/mac/tweak_info_plist.py to not rely on environment variables.

chrome/chrome.gyp

 # 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.
 {
   'variables': {
     'chromium_code': 1,
 
     # Define the common dependencies that contain all the actual
     # Chromium functionality.  This list gets pulled in below by
     # the link of the actual chrome (or chromium) executable on
@@ skipping 210 matching lines @@
               ],
             },
             {
               # Modify the Info.plist as needed.  The script explains why this
               # is needed.  This is also done in the chrome and chrome_dll
               # targets.  In this case, --breakpad=0, --keystone=0, and --scm=0
               # are used because Breakpad, Keystone, and SCM keys are
               # never placed into the helper.
               'postbuild_name': 'Tweak Info.plist',
               'action': ['<(tweak_info_plist_path)',
+                         '--plist=${TARGET_BUILD_DIR}/${INFOPLIST_PATH}',
                          '--breakpad=0',
                          '--keystone=0',
                          '--scm=0'],
             },
           ],
           'conditions': [
             ['mac_breakpad==1', {
               'variables': {
                 # A real .dSYM is needed for dump_syms to operate on.
                 'mac_real_dsym': 1,
@@ skipping 570 matching lines @@
                 # expired. crbug.com/577698
                 '../components/components.gyp:startup_metric_utils_common',
               ],
             }],
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }