Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/b810910..876f9d1

Rolling v8/tools/clang: https://chromium.googlesource.com/chromium/src/tools/clang/+log/3be402c..a1420b8

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

Change-Id: I798d723b736faa1eff4cd50f34e7af9bc3f36a26
Reviewed-on: https://chromium-review.googlesource.com/612842Reviewed-by: v8 autoroll <v8-autoroll@chromium.org>
Commit-Queue: v8 autoroll <v8-autoroll@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47327}