message: Try to fix windows build failure.
  The "\" might be converted to "\\" in windows and causing copybara failure during conversion.
diff: @@ -128,8 +128,8 @@ def get_plugin_args(
  ]
  def _get_staged_proto_file(context, source_file):
  - if source_file.dirname == context.label.package or \
  - is_in_virtual_imports(source_file):
  + if (source_file.dirname == context.label.package or
  + is_in_virtual_imports(source_file)):
  return source_file
  else:
  copied_proto = context.actions.declare_file(source_file.basename)
  