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

Revert of Fix downloading LLVM Gold plugin in the case, when Clang is up to date. (patchset #1 id:1 of https://codereview.chromium.org/1491203003/ )

Reason for revert:
This breaks Codesearch bots.

Original issue's description:
> Fix downloading LLVM Gold plugin in the case, when Clang is up to date.
>
> The script should download LLVM Gold plugin, if it's missing, even if the
> main Clang toolchain is up to date. This change is to match update.py
> functionality with the gone update.sh.
>
> BUG=464797,494442
>
> Committed: https://crrev.com/7ff79f9569429444dabdb6d5024918bc548916b3
> Cr-Commit-Position: refs/heads/master@{#362803}

TBR=thakis@chromium.org,krasin@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=464797,494442

Review URL: https://codereview.chromium.org/1494883004

Cr-Commit-Position: refs/heads/master@{#362938}

tools/clang/scripts/update.py

@@ -301,17 +301,9 @@ 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 '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
+    print 'Already up to date.'
+    return 0
 
   # Reset the stamp file in case the build is unsuccessful.
   WriteStampFile('')
@@ -339,7 +331,10 @@ 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 need_gold_plugin:
+      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', '')):
         RunCommand(['python', CHROMIUM_DIR+'/build/download_gold_plugin.py'])
       WriteStampFile(PACKAGE_VERSION)
       return 0