Rolling v8/buildtools to b747a9e091cb8212a62343258406eaf53a6c032e

Rolling v8/tools/clang to 58b11d197b1c5fec39a6ec374c21b3d3a5bf557b

Rolling v8/tools/swarming_client to 9cdd76171e517a430a72dcd7d66ade67e109aa00

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

Review URL: https://codereview.chromium.org/1493273004

Cr-Commit-Position: refs/heads/master@{#32593}