Fixup jumbo.gni (-Wno-subobject-linkage)

build/jumbo.py

 #!/usr/bin/env python
 #
 # Copyright 2016 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 script creates a "jumbo" file which merges all incoming files
 for compiling.
 
 """
@@ skipping 26 matching lines @@
     written_inputs = 0
     for output_index, output_file in enumerate(args.outputs):
         # TODO: Check if the file is right already and then do not update it.
         with open(output_file, "w") as out:
             out.write("/* This is a Jumbo file. Don't edit. */\n\n")
             out.write("/* Generated with jumbo.py. */\n\n")
             input_limit = (output_index + 1) * input_count / output_count
             while written_inputs < input_limit:
                 filename = inputs[written_inputs]
                 written_inputs += 1
-                if filename.endswith(".h"):
+                if filename.endswith(".h") or filename.endswith(".mm"):
                     continue
 
                 out.write("#include \"%s\"\n" % filename)
 
     if args.verbose:
         print("Generated %s (%d files) based on %s" % (str(args.outputs),
                                                        written_inputs,
                                                        args.file_list))
 
 if __name__ == "__main__":
     main()