Update from https://crrev.com/329939

tools/clang/scripts/update.sh

 #!/usr/bin/env bash
 # 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 will check out llvm and clang into third_party/llvm and build it.
 
 # Do NOT CHANGE this if you don't know what you're doing -- see
 # https://code.google.com/p/chromium/wiki/UpdatingClang
 # Reverting problematic clang rolls is safe, though.
@@ skipping 38 matching lines @@
 if [[ -z "$GYP_GENERATORS" ]]; then
   GYP_GENERATORS=
 fi
 
 
 # Die if any command dies, error on undefined variable expansions.
 set -eu
 
 
 if [[ -n ${LLVM_FORCE_HEAD_REVISION:-''} ]]; then
-  # Use a real version number rather than HEAD to make sure that
-  # --print-revision, stamp file logic, etc. all works naturally.
+  # Use a real revision number rather than HEAD to make sure that the stamp file
+  # logic works.
   CLANG_REVISION=$(svn info "$LLVM_REPO_URL" \
-      | grep 'Last Changed Rev' | awk '{ printf $4; }')
+      | grep 'Revision:' | awk '{ printf $2; }')
   PACKAGE_VERSION="${CLANG_REVISION}-0"
 fi
 
 OS="$(uname -s)"
 
 # Parse command line options.
 if_needed=
 force_local_build=
 run_tests=
 bootstrap=
@@ skipping 11 matching lines @@
     --bootstrap)
       bootstrap=yes
       ;;
     --if-needed)
       if_needed=yes
       ;;
     --force-local-build)
       force_local_build=yes
       ;;
     --print-revision)
-      echo $PACKAGE_VERSION
+      if [[ -n ${LLVM_FORCE_HEAD_REVISION:-''} ]]; then
+        svn info "$LLVM_DIR" | grep 'Revision:' | awk '{ printf $2; }'
+      else
+        echo $PACKAGE_VERSION
+      fi
       exit 0
       ;;
     --run-tests)
       run_tests=yes
       ;;
     --without-android)
       with_android=
       ;;
     --without-patches)
       with_patches=
@@ skipping 591 matching lines @@
 
 if [[ -n "$run_tests" ]]; then
   # Run Chrome tool tests.
   ninja -C "${LLVM_BUILD_DIR}" cr-check-all
   # Run the LLVM and Clang tests.
   ninja -C "${LLVM_BUILD_DIR}" check-all
 fi
 
 # After everything is done, log success for this revision.
 echo "${PACKAGE_VERSION}" > "${STAMP_FILE}"