Update V8 DEPS.

Rolling v8/tools/clang to 64370e74764d1fa9f50151d0e6025b0399370100

TBR=machenbach@chromium.org

Review URL: https://codereview.chromium.org/1320293002

Cr-Commit-Position: refs/heads/master@{#30472}

DEPS

@@ -18,7 +18,7 @@ deps = {
   "v8/testing/gmock":
     Var("git_url") + "/external/googlemock.git" + "@" + "0421b6f358139f02e102c9c332ce19a33faf75be",
   "v8/tools/clang":
-    Var("git_url") + "/chromium/src/tools/clang.git" + "@" + "5439585778385813bc7711f3d6b7035b9eb78572",
+    Var("git_url") + "/chromium/src/tools/clang.git" + "@" + "64370e74764d1fa9f50151d0e6025b0399370100",
 }
 
 deps_os = {