Update V8 DEPS.

Rolling v8/buildtools to 4995faa4a7ad968f1fa1917c26edd5cea295582f

Rolling v8/tools/clang to 3569efa494f668b68bd13835ab4f197f6a51b84a

TBR=machenbach@chromium.org

Review URL: https://codereview.chromium.org/801783003

Cr-Commit-Position: refs/heads/master@{#25799}