Let the users skip the gold plugin installation

tools/clang/scripts/update.py

 #!/usr/bin/env python
 # 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.
 
 """This script is used to download prebuilt clang binaries.
 
 It is also used by package.py to build the prebuilt clang binaries."""
 
 import argparse
@@ skipping 65 matching lines @@
     CHROMIUM_DIR, 'third_party', 'android_tools', 'ndk')
 
 # URL for pre-built binaries.
 CDS_URL = os.environ.get('CDS_CLANG_BUCKET_OVERRIDE',
     'https://commondatastorage.googleapis.com/chromium-browser-clang')
 
 LLVM_REPO_URL='https://llvm.org/svn/llvm-project'
 if 'LLVM_REPO_URL' in os.environ:
   LLVM_REPO_URL = os.environ['LLVM_REPO_URL']
 
+skip_gold_plugin = 'SKIP_GOLD_PLUGIN' in os.environ
+
 # Bump after VC updates.
 DIA_DLL = {
   '2013': 'msdia120.dll',
   '2015': 'msdia140.dll',
 }
 
 
 def DownloadUrl(url, output_file):
   """Download url into output_file."""
   CHUNK_SIZE = 4096
@@ skipping 295 matching lines @@
   if version_out != VERSION:
     print ('unexpected clang version %s (not %s), update VERSION in update.py'
            % (version_out, VERSION))
     sys.exit(1)
 
 
 def UpdateClang(args):
   print 'Updating Clang to %s...' % PACKAGE_VERSION
 
   # Required for LTO, which is used when is_official_build = true.
-  need_gold_plugin = sys.platform.startswith('linux')
+  need_gold_plugin = sys.platform.startswith('linux') and not skip_gold_plugin
 
   if ReadStampFile() == PACKAGE_VERSION and not args.force_local_build:
     print 'Clang is already up to date.'
     if not need_gold_plugin or os.path.exists(
         os.path.join(LLVM_BUILD_DIR, "lib/LLVMgold.so")):
       return 0
 
   # Reset the stamp file in case the build is unsuccessful.
   WriteStampFile('')
 
@@ skipping 494 matching lines @@
     args.force_local_build = True
     if 'OS=android' not in os.environ.get('GYP_DEFINES', ''):
       # Only build the Android ASan rt on ToT bots when targetting Android.
       args.with_android = False
 
   return UpdateClang(args)
 
 
 if __name__ == '__main__':
   sys.exit(main())