V8: Let peek-gn use mb to reuse v8-side configs.

scripts/slave/recipe_modules/v8/resources/patch_mb_config.py

Index: scripts/slave/recipe_modules/v8/resources/patch_mb_config.py
diff --git a/scripts/slave/recipe_modules/v8/resources/patch_mb_config.py b/scripts/slave/recipe_modules/v8/resources/patch_mb_config.py
new file mode 100755
index 0000000000000000000000000000000000000000..a884b76605818c2e2a6181384b573517dafedeec
--- /dev/null
+++ b/scripts/slave/recipe_modules/v8/resources/patch_mb_config.py
@@ -0,0 +1,15 @@
+#!/usr/bin/env python
+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Script that makes an mb config use gn where it's supposed to use gyp.
+
+This is used to run gn on all gyp bots as an fyi step.
+"""
+
+import sys
+
+with open(sys.argv[1]) as f:
+  with open(sys.argv[2], 'w') as g:
+    g.write(f.read().replace("'type': 'gyp'", "'type': 'gn'"))