Fix downloading LLVM Gold plugin in the case, when Clang is up to date.

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 aca7cb9a79c0d0e791cf2a6a835f081977488720..4bf1bab35f3bf899ffeb0f2c2b7dfdc500997573 100755
--- a/tools/clang/scripts/update.py
+++ b/tools/clang/scripts/update.py
@@ -301,9 +301,17 @@ def GetVSVersion():
 
 def UpdateClang(args):
   print 'Updating Clang to %s...' % PACKAGE_VERSION
+
+  need_gold_plugin = 'LLVM_DOWNLOAD_GOLD_PLUGIN' in os.environ or (
+      sys.platform.startswith('linux') and
+      'buildtype=Official' in os.environ.get('GYP_DEFINES', '') and
+      'branding=Chrome' in os.environ.get('GYP_DEFINES', ''))
+
   if ReadStampFile() == PACKAGE_VERSION:
-    print 'Already up to date.'
-    return 0
+    print 'Clang is already up to date.'

[Adrian Kuegel, 2015/12/03 09:29:26]

I think this early return breaks the case if you want to compile clang tools,
like we do on the Codesearch bots:
https://build.chromium.org/p/chromium.infra.cron/builders/Chromium%20Linux%20...
Look at the "compile translation_unit clang tool" step, it does an early return
while in fact it should compile the clang tool.

+    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('')
@@ -331,10 +339,7 @@ def UpdateClang(args):
       # Download the gold plugin if requested to by an environment variable.
       # This is used by the CFI ClusterFuzz bot, and it's required for official
       # builds on linux.
-      if 'LLVM_DOWNLOAD_GOLD_PLUGIN' in os.environ or (
-          sys.platform.startswith('linux') and
-          'buildtype=Official' in os.environ.get('GYP_DEFINES', '') and
-          'branding=Chrome' in os.environ.get('GYP_DEFINES', '')):
+      if need_gold_plugin:
         RunCommand(['python', CHROMIUM_DIR+'/build/download_gold_plugin.py'])
       WriteStampFile(PACKAGE_VERSION)
       return 0