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

build/config/ios/find_signing_identity.py

+#!/usr/bin/python
+# Copyright (c) 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.
+
+import subprocess
+import sys
+import re
+
+def ListIdentities():
+  return subprocess.check_output([
+    '/usr/bin/env',
+    'xcrun',
+    'security',
+    'find-identity',
+    '-v',
+    '-p',
+    'codesigning',
+  ]).strip()
+
+
+def FindValidIdentity():
+  lines = ListIdentities().splitlines()
+  # Look for something like "2) XYZ "iPhone Developer: Name (ABC)""
+  exp = re.compile('.*\) ([A-F|0-9]*)(.*)')
+  for line in lines:
+    res = exp.match(line)
+    if res is None:
+      continue
+    if "iPhone Developer: Google Development" in res.group(2):
+      return res.group(1)
+  return ""
+
+
+if __name__ == '__main__':
+  print FindValidIdentity()