[Mac/GN] Fix rebuilds when changing framework_version of a mac_framework_bundle.

build/config/mac/prepare_framework_version.py

Index: build/config/mac/prepare_framework_version.py
diff --git a/build/config/mac/prepare_framework_version.py b/build/config/mac/prepare_framework_version.py
new file mode 100644
index 0000000000000000000000000000000000000000..1faee19bcc0ba9e19440e95be79f3e2b610e902f
--- /dev/null
+++ b/build/config/mac/prepare_framework_version.py
@@ -0,0 +1,34 @@
+# 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.
+
+import os.path
+import shutil
+import sys
+
+# Ensures that the current version matches the last-produced version, which is
+# stored in the version_file. If it does not, then the framework_root_dir is
+# obliterated.
+# Usage: python prepare_framework_version.py out/obj/version_file \
+#                                            out/Framework.framework \
+#                                            'A'
+
+def PrepareFrameworkVersion(version_file, framework_root_dir, version):
+  try:
+    with open(version_file, 'r') as f:
+      current_version = f.read()
+      if current_version == version:
+        return
+  except IOError:
+    pass
+
+  if os.path.exists(framework_root_dir):
+    shutil.rmtree(framework_root_dir)
+
+  f = open(version_file, 'w+')
+  f.write(version)
+  f.close()
+
+
+if __name__ == '__main__':
+  PrepareFrameworkVersion(sys.argv[1], sys.argv[2], sys.argv[3])