Rolling v8/buildtools to 81863fe70639e85606b541d9d36e9e98c96b957e

Rolling v8/tools/clang to fe8d232767c63ce43873ffef101063a5791d171e

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

Review URL: https://codereview.chromium.org/1561063002

Cr-Commit-Position: refs/heads/master@{#33134}