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

build/ls.py

+#!/usr/bin/python
+# Copyright 2015 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.
+
+"""Recursively list files of the target directory. Ignores dot files."""
+
+import argparse
+import os
+import sys
+
+def main(target_directory):
+  for root, dirs, files in os.walk(target_directory):
+    files = [f for f in files if not f[0] == '.']
+    dirs[:] = [d for d in dirs if not d[0] == '.']
+    for f in files:
+      path = os.path.join(root, f)
+      print path
+
+if __name__ == '__main__':
+  parser = argparse.ArgumentParser(
+      description="Recursively list files of the target directory")
+  parser.add_argument("--target-directory",
+                      dest="target_directory",
+                      metavar="<target-directory>",
+                      type=str,
+                      required=True,
+                      help="The target directory")
+
+  args = parser.parse_args()
+  sys.exit(main(args.target_directory))