[gn] Skip gyp_v8 when gn should run

gypfiles/gyp_v8

 #!/usr/bin/env python
 #
 # 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
@@ skipping 100 matching lines @@
       (x86_runtime, x64_runtime))
 
   if rc != 0:
     print 'Error running GYP'
     sys.exit(rc)
 
 
 if __name__ == '__main__':
   args = sys.argv[1:]
 
+  if int(os.environ.get('GYP_CHROMIUM_NO_ACTION', 0)):
+    print 'Skipping gyp_v8 due to GYP_CHROMIUM_NO_ACTION env var.'
+    sys.exit(0)
+
   gyp_environment.set_environment()
 
   # This could give false positives since it doesn't actually do real option
   # parsing.  Oh well.
   gyp_file_specified = False
   for arg in args:
     if arg.endswith('.gyp'):
       gyp_file_specified = True
       break
 
@@ skipping 41 matching lines @@
 
   gyp_defines = os.environ.get('GYP_DEFINES', '')
 
   # Automatically turn on crosscompile support for platforms that need it.
   if all(('ninja' in gyp_generators,
           'OS=android' in gyp_defines,
           'GYP_CROSSCOMPILE' not in os.environ)):
     os.environ['GYP_CROSSCOMPILE'] = '1'
 
   run_gyp(gyp_args)