Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/475d5b3..67604e1

Rolling v8/buildtools: https://chromium.googlesource.com/chromium/buildtools/+log/5fd6695..39b1db2

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

Review-Url: https://codereview.chromium.org/2397993002
Cr-Commit-Position: refs/heads/master@{#40019}