Don't return early in case force-local-builds is passed.

BUG=
TBR=thakis@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/1492053005

Cr-Commit-Position: refs/heads/master@{#362955}

tools/clang/scripts/update.py

@@ -307,7 +307,7 @@ def UpdateClang(args):
       'buildtype=Official' in os.environ.get('GYP_DEFINES', '') and
       'branding=Chrome' in os.environ.get('GYP_DEFINES', ''))
 
-  if ReadStampFile() == PACKAGE_VERSION:
+  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")):