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

build/cp.py

+#!/usr/bin/env python
+# Copyright (c) 2012 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.
+
+"""Copy a file.
+
+This module works much like the cp posix command - it takes 2 arguments:
+(src, dst) and copies the file with path |src| to |dst|.
+"""
+
+import os
+import shutil
+import sys
+
+
+def Main(src, dst):
+  # Use copy instead of copyfile to ensure the executable bit is copied.
+  return shutil.copy(src, os.path.normpath(dst))
+
+
+if __name__ == '__main__':
+  sys.exit(Main(sys.argv[1], sys.argv[2]))