Rolling v8/build/gyp to 4a9b712d5cb4a5ba7a9950128a7219569caf7263

Rolling v8/buildtools to d4dd4f79f60bf019625b3a1436979b0a42c892df

Rolling v8/tools/clang to 5309ba9a6f1e56592860a623db451aef00ae941d

TBR=machenbach@chromium.org

Review URL: https://codereview.chromium.org/978193002

Cr-Commit-Position: refs/heads/master@{#27002}