Update V8 DEPS.
Update V8 DEPS.

Rolling v8/tools/clang to 5439585778385813bc7711f3d6b7035b9eb78572

TBR=machenbach@chromium.org

Review URL: https://codereview.chromium.org/1307783002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#30279}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh