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

build/ios/clean_env.py

Index: build/ios/clean_env.py
diff --git a/build/ios/clean_env.py b/build/ios/clean_env.py
new file mode 100755
index 0000000000000000000000000000000000000000..548e2b92eefdd6fd1c9ef65945afaf29e2d3a408
--- /dev/null
+++ b/build/ios/clean_env.py
@@ -0,0 +1,77 @@
+#!/usr/bin/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.
+
+import os
+import sys
+
+def Main(argv):
+  """This is like 'env -i', but it uses a whitelist of env variables to allow
+  through to the command being run.  It attempts to strip off Xcode-added
+  values from PATH.
+  """
+  # Note: An attempt was made to do something like: env -i bash -lc '[command]'
+  # but that fails to set the things set by login (USER, etc.), so instead
+  # the only approach that seems to work is to have a whitelist.
+  env_key_whitelist = (
+    'HOME',
+    'LOGNAME',
+    # 'PATH' added below (but filtered).
+    'PWD',
+    'SHELL',
+    'TEMP',
+    'TMPDIR',
+    'USER'
+  )
+
+  # Need something to run.
+  # TODO(lliabraa): Make this output a usage string and exit (here and below).
+  assert(len(argv) > 0)
+
+  add_to_path = [];
+  first_entry = argv[0];
+  if first_entry.startswith('ADD_TO_PATH='):
+    argv = argv[1:];
+    add_to_path = first_entry.replace('ADD_TO_PATH=', '', 1).split(':')
+
+  # Still need something to run.
+  assert(len(argv) > 0)
+
+  clean_env = {}
+
+  # Pull over the whitelisted keys.
+  for key in env_key_whitelist:
+    val = os.environ.get(key, None)
+    if not val is None:
+      clean_env[key] = val
+
+  # Collect the developer dir as set via Xcode, defaulting it.
+  dev_prefix = os.environ.get('DEVELOPER_DIR', '/Developer/')
+  if dev_prefix[-1:] != '/':
+    dev_prefix += '/'
+
+  # Now pull in PATH, but remove anything Xcode might have added.
+  initial_path = os.environ.get('PATH', '')
+  filtered_chunks = \
+      [x for x in initial_path.split(':') if not x.startswith(dev_prefix)]
+  if filtered_chunks:
+    clean_env['PATH'] = ':'.join(add_to_path + filtered_chunks)
+
+  # Add any KEY=VALUE args before the command to the cleaned environment.
+  args = argv[:]
+  while '=' in args[0]:
+    (key, val) = args[0].split('=', 1)
+    clean_env[key] = val
+    args = args[1:]
+
+  # Still need something to run.
+  assert(len(args) > 0)
+
+  # Off it goes...
+  os.execvpe(args[0], args, clean_env)
+  # Should never get here, so return a distinctive, non-zero status code.
+  return 66
+
+if __name__ == '__main__':
+  sys.exit(Main(sys.argv[1:]))