Update V8 DEPS.

Rolling v8/buildtools to 277db9302c7ff55beee2a9daf380675dc03bea83

TBR=machenbach@chromium.org,vogelheim@chromium.org,hablich@chromium.org

Review URL: https://codereview.chromium.org/1454553003

Cr-Commit-Position: refs/heads/master@{#32021}

DEPS

@@ -12,7 +12,7 @@ deps = {
   "v8/third_party/icu":
     Var("git_url") + "/chromium/deps/icu.git" + "@" + "42c58d4e49f2250039f0e98d43e0b76e8f5ca024",
   "v8/buildtools":
-    Var("git_url") + "/chromium/buildtools.git" + "@" + "3ba3ca22ec610fe95683f6bfdeea9d90c768abd7",
+    Var("git_url") + "/chromium/buildtools.git" + "@" + "277db9302c7ff55beee2a9daf380675dc03bea83",
   "v8/tools/swarming_client":
     Var('git_url') + '/external/swarming.client.git' + '@' + "8fce79620b04bbe5415ace1103db27505bdc4c06",
   "v8/testing/gtest":