Rolling v8/tools/clang to 668876fb488c6e3c5860a367b7d9a7fb8821df76

TBR=machenbach@chromium.org,vogelheim@chromium.org,hablich@chromium.org

Review URL: https://codereview.chromium.org/1513903003

Cr-Commit-Position: refs/heads/master@{#32732}