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

build/download_nacl_toolchains.py

Index: build/download_nacl_toolchains.py
diff --git a/build/download_nacl_toolchains.py b/build/download_nacl_toolchains.py
new file mode 100755
index 0000000000000000000000000000000000000000..b99b940f9c798d9ff3670e08e774e9d6a1b27e3f
--- /dev/null
+++ b/build/download_nacl_toolchains.py
@@ -0,0 +1,59 @@
+#!/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.
+
+"""Shim to run nacl toolchain download script only if there is a nacl dir."""
+
+import os
+import shutil
+import sys
+
+
+def Main(args):
+  # Exit early if disable_nacl=1.
+  if 'disable_nacl=1' in os.environ.get('GYP_DEFINES', ''):
+    return 0
+  script_dir = os.path.dirname(os.path.abspath(__file__))
+  src_dir = os.path.dirname(script_dir)
+  nacl_dir = os.path.join(src_dir, 'native_client')
+  nacl_build_dir = os.path.join(nacl_dir, 'build')
+  package_version_dir = os.path.join(nacl_build_dir, 'package_version')
+  package_version = os.path.join(package_version_dir, 'package_version.py')
+  if not os.path.exists(package_version):
+    print "Can't find '%s'" % package_version
+    print 'Presumably you are intentionally building without NativeClient.'
+    print 'Skipping NativeClient toolchain download.'
+    sys.exit(0)
+  sys.path.insert(0, package_version_dir)
+  import package_version
+
+  # BUG:
+  # We remove this --optional-pnacl argument, and instead replace it with
+  # --no-pnacl for most cases.  However, if the bot name is an sdk
+  # bot then we will go ahead and download it.  This prevents increasing the
+  # gclient sync time for developers, or standard Chrome bots.
+  if '--optional-pnacl' in args:
+    args.remove('--optional-pnacl')
+    use_pnacl = False
+    buildbot_name = os.environ.get('BUILDBOT_BUILDERNAME', '')
+    if 'pnacl' in buildbot_name and 'sdk' in buildbot_name:
+      use_pnacl = True
+    if use_pnacl:
+      print '\n*** DOWNLOADING PNACL TOOLCHAIN ***\n'
+    else:
+      args = ['--exclude', 'pnacl_newlib'] + args
+
+  # Only download the ARM gcc toolchain if we are building for ARM
+  # TODO(olonho): we need to invent more reliable way to get build
+  # configuration info, to know if we're building for ARM.
+  if 'target_arch=arm' not in os.environ.get('GYP_DEFINES', ''):
+      args = ['--exclude', 'nacl_arm_newlib'] + args
+
+  package_version.main(args)
+
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(Main(sys.argv[1:]))