message: Update calls to deprecated Starlark functions/arguments
diff: @@ -200,8 +200,7 @@ symlink = rule(
  attrs = {
  "src": attr.label(
  mandatory = True,
  - allow_files = True,
  - single_file = True,
  + allow_single_file = True,
  ),
  "out": attr.output(mandatory = True),
  },
  