Rolling v8/build: https://chromium.googlesource.com/chromium/src/build/+log/d9a25a7..9ce44b9

Rolling v8/tools/clang: https://chromium.googlesource.com/chromium/src/tools/clang/+log/34762ec..7185692

This also ports https://chromium-review.googlesource.com/c/582976

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

Change-Id: I6436dd50b7cee016d1cc2d5f48d2d27e9025276d
Reviewed-on: https://chromium-review.googlesource.com/584171
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: v8 autoroll <v8-autoroll@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46855}