Update V8 DEPS.
Update V8 DEPS.

Rolling v8/tools/clang to c9a343c6a8065127989a05fe2a3fc76c26ad8102

TBR=machenbach@chromium.org

Review URL: https://codereview.chromium.org/1274553002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#30018}

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