Update V8 DEPS.

Rolling v8/buildtools to f7310ee61725e68b1c8921e381830362cf4f0999

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

Review URL: https://codereview.chromium.org/1342063002

Cr-Commit-Position: refs/heads/master@{#30724}

DEPS

@@ -12,7 +12,7 @@ deps = {
   "v8/third_party/icu":
     Var("git_url") + "/chromium/deps/icu.git" + "@" + "6b3ce817f8e828c3b7a577d2395f0882eb56ef18",
   "v8/buildtools":
-    Var("git_url") + "/chromium/buildtools.git" + "@" + "565d04e8741429fb1b4f26d102f2c6c3b849edeb",
+    Var("git_url") + "/chromium/buildtools.git" + "@" + "f7310ee61725e68b1c8921e381830362cf4f0999",
   "v8/testing/gtest":
     Var("git_url") + "/external/googletest.git" + "@" + "9855a87157778d39b95eccfb201a9dc90f6d61c6",
   "v8/testing/gmock":