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

build/check_return_value.py

Index: build/check_return_value.py
diff --git a/build/check_return_value.py b/build/check_return_value.py
new file mode 100755
index 0000000000000000000000000000000000000000..c659d1e9674ab96af49c3fb2dea8b061ecef162a
--- /dev/null
+++ b/build/check_return_value.py
@@ -0,0 +1,17 @@
+#!/usr/bin/env python
+# Copyright 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.
+
+"""This program wraps an arbitrary command and prints "1" if the command ran
+successfully."""
+
+import os
+import subprocess
+import sys
+
+devnull = open(os.devnull, 'wb')
+if not subprocess.call(sys.argv[1:], stdout=devnull, stderr=devnull):
+  print 1
+else:
+  print 0