IDL build: factor out global objects action into a GYP template

Source/bindings/bindings.gypi

 # Copyright 2014 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.
 
 {
     'includes': [
         'v8/v8.gypi',
     ],
     'variables': {
         'bindings_dir': '.',
         'bindings_unittest_files': [
             '<@(bindings_v8_unittest_files)',
         ],
-        'conditions': [
-            # The bindings generator can skip writing generated files if they
-            # are identical to the already existing file, which avoids
-            # recompilation.  However, a dependency (earlier build step) having
-            # a newer timestamp than an output (later build step) confuses some
-            # build systems, so only use this on ninja, which explicitly
-            # supports this use case (gyp turns all actions into ninja restat
-            # rules).
-            ['"<(GENERATOR)"=="ninja"', {
-              'write_file_only_if_changed': '1',
-            }, {
-              'write_file_only_if_changed': '0',
-            }],
-        ],
     },
 }