Let the users skip the gold plugin installation

tools/clang/scripts/update.py

Index: tools/clang/scripts/update.py
diff --git a/tools/clang/scripts/update.py b/tools/clang/scripts/update.py
index 35e57c9023b27f29de05e59d907ddeacc303db32..eff0afbea860256bde5fb4f6a057be5c7eb2facd 100755
--- a/tools/clang/scripts/update.py
+++ b/tools/clang/scripts/update.py
@@ -83,6 +83,8 @@ 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',
@@ -398,7 +400,7 @@ 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.'