Rolling v8/build/gyp to 29e94a3285ee899d14d5e56a6001682620d3778f

Rolling v8/tools/clang to dc8f173e7fe10badbd9e29cd6eadc32ec552e691

TBR=machenbach@chromium.org

Review URL: https://codereview.chromium.org/1156373003

Cr-Commit-Position: refs/heads/master@{#28668}