The dynamic services SDK produces a fat Mach binary of x64 and arm64 variants.

engine/src/flutter/sky/tools/lipo.py

@@ -0,0 +1,52 @@
+#!/usr/bin/env 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.
+
+import argparse
+import subprocess
+import sys
+import os
+
+
+def MakeStamp(stamp_path):
+  dir_name = os.path.dirname(stamp_path)
+
+  if not os.path.isdir(dir_name):
+    os.makedirs()
+
+  with open(stamp_path, 'a'):
+    os.utime(stamp_path, None)
+
+
+def main():
+  parser = argparse.ArgumentParser(
+      description='Creates a FAT Mach binary')
+
+  parser.add_argument('--path', action='append', dest='paths',
+      default=[], help='The path to a Mach binary')
+  parser.add_argument('--output', type=str)
+  parser.add_argument('--stamp', type=str)
+
+  args = parser.parse_args()
+
+  cmd = [
+    '/usr/bin/env',
+    'xcrun',
+    'lipo',
+  ]
+
+  cmd.extend(args.paths)
+
+  cmd.extend([
+    '-create',
+    '-output',
+    args.output,
+  ])
+
+  subprocess.check_call(cmd)
+
+  MakeStamp(args.stamp)
+
+if __name__ == '__main__':
+  sys.exit(main())