Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/a7e9a83..d7db4b1

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

Change-Id: I4927c9c2c90853b8587ac1f5146bb91b4e745b7d
Reviewed-on: https://chromium-review.googlesource.com/972640
Commit-Queue: v8 autoroll <v8-autoroll@chromium.org>
Reviewed-by: v8 autoroll <v8-autoroll@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52087}