Disable GN.

This deletes the hooks and running GN to produce GYP files while the project is on hold.

BUG=350974
TBR=jam

Review URL: https://codereview.chromium.org/193053003

git-svn-id: http://src.chromium.org/svn/trunk/src/build@256035 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

gyp_chromium

@@ -550,8 +550,9 @@ if __name__ == '__main__':
           'GYP_CROSSCOMPILE' not in os.environ)):
     os.environ['GYP_CROSSCOMPILE'] = '1'
 
-  if not RunGN(gn_vars_dict):
-    sys.exit(1)
+  # TODO(brettw) bug 350974 either turn back on GN or delete all of this code.
+  #if not RunGN(gn_vars_dict):
+  #  sys.exit(1)
   args.extend(
       ['-I' + i for i in additional_include_files(supplemental_includes, args)])