Update V8 DEPS.

DEPS

 # Note: The buildbots evaluate this file with CWD set to the parent
 # directory and assume that the root of the checkout is in ./v8/, so
 # all paths in here must match this assumption.
 
 vars = {
   "git_url": "https://chromium.googlesource.com",
 }
 
 deps = {
   "v8/build/gyp":
     Var("git_url") + "/external/gyp.git" + "@" + "01528c7244837168a1c80f06ff60fa5a9793c824",
   "v8/third_party/icu":
     Var("git_url") + "/chromium/deps/icu.git" + "@" + "94e4b770ce2f6065d4261d29c32683a6099b9d93",
   "v8/buildtools":
-    Var("git_url") + "/chromium/buildtools.git" + "@" + "5fc8d3943e163ee627c8af50366c700c0325bba2",
+    Var("git_url") + "/chromium/buildtools.git" + "@" + "ef7f1f539cff0441c4401d8c052e54cfd01bff07",
   "v8/tools/swarming_client":
     Var('git_url') + '/external/swarming.client.git' + '@' + "e4c0e242eeec361886ed2b89591a505ebe24db43",
   "v8/testing/gtest":
     Var("git_url") + "/external/github.com/google/googletest.git" + "@" + "6f8a66431cb592dad629028a50b3dd418a408c87",
   "v8/testing/gmock":
     Var("git_url") + "/external/googlemock.git" + "@" + "0421b6f358139f02e102c9c332ce19a33faf75be",
   "v8/test/test262/data":
     Var("git_url") + "/external/github.com/tc39/test262.git" + "@" + "26e6fd7c1779a63913cc7720cbc6c87b3b7b3285",
   "v8/tools/clang":
     Var("git_url") + "/chromium/src/tools/clang.git" + "@" + "a56c9063d582660d29b32f967ce20875c589fc3e",
@@ skipping 127 matching lines @@
     'name': 'clang',
     'pattern': '.',
     'action': ['python', 'v8/tools/clang/scripts/update.py', '--if-needed'],
   },
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     "pattern": ".",
     "action": ["python", "v8/build/gyp_v8"],
   },
 ]