Generate shim headers when using system v8.

tools/gyp/v8.gyp

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 973 matching lines @@
         {
           'target_name': 'v8',
           'type': 'none',
           'conditions': [
             ['want_separate_host_toolset==1', {
               'toolsets': ['host', 'target'],
             }, {
               'toolsets': ['target'],
             }],
           ],
+          'variables': {
+            'shim_headers_path': '<(SHARED_INTERMEDIATE_DIR)/shim_headers/<(_target_name)/<(_toolset)',
+          },
+          'include_dirs++': [
+            '<(shim_headers_path)',
+          ],
+          'direct_dependent_settings': {
+            'include_dirs+++': [
+              '<(shim_headers_path)',
+            ],
+          },
+          'actions': [
+            {
+              'variables': {
+                'generator_path': '../../../tools/generate_shim_headers/generate_shim_headers.py',
+                'generator_args': [
+                  '--headers-root', '../../include',
+                  '--output-directory', '<(shim_headers_path)',
+                  'v8-debug.h',
+                  'v8-preparser.h',
+                  'v8-profiler.h',
+                  'v8-testing.h',
+                  'v8.h',
+                  'v8stdint.h',
+                ],
+              },
+              'action_name': 'generate_<(_target_name)_shim_headers',
+              'inputs': [
+                '<(generator_path)',
+              ],
+              'outputs': [
+                '<!@pymod_do_main(generate_shim_headers <@(generator_args) --outputs)',
+              ],
+              'action': ['python',
+                         '<(generator_path)',
+                         '<@(generator_args)',
+                         '--generate',
+              ],
+              'message': 'Generating <(_target_name) shim headers.',
+            },
+          ],
           'link_settings': {
             'libraries': [
               '-lv8',
             ],
           },
         },
         {
           'target_name': 'v8_shell',
           'type': 'none',
           'conditions': [
             ['want_separate_host_toolset==1', {
               'toolsets': ['host'],
             }, {
               'toolsets': ['target'],
             }],
           ],
           'dependencies': [
             'v8'
           ],
         },
       ],
     }],
   ],
 }