Add a snapshot of flutter/engine/src/build to our sdk

build/get_sdk_extras_packages.py

Index: build/get_sdk_extras_packages.py
diff --git a/build/get_sdk_extras_packages.py b/build/get_sdk_extras_packages.py
new file mode 100755
index 0000000000000000000000000000000000000000..a90b8a8b4a4f224f73abf8e45dadbe16622d89d5
--- /dev/null
+++ b/build/get_sdk_extras_packages.py
@@ -0,0 +1,24 @@
+#!/usr/bin/env python
+# Copyright (c) 2014 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 json
+import os
+import sys
+
+SDK_EXTRAS_JSON_FILE = os.path.join(os.path.dirname(__file__),
+                                    'android_sdk_extras.json')
+
+def main():
+  with open(SDK_EXTRAS_JSON_FILE) as json_file:
+    packages = json.load(json_file)
+
+  out = []
+  for package in packages:
+    out.append(package['package_id'])
+
+  print ','.join(out)
+
+if __name__ == '__main__':
+  sys.exit(main())