message: Don't parse more than one argument to -O
diff: @@ -110,7 +110,7 @@ struct Args {
  /// macros[=<true/false>] - Enable or disable macros (experimental).
  ///
  /// bytecode[=<true/false>] - Enable or disable bytecode caching (experimental).
  - #[structopt(name = "option", short = "O")]
  + #[structopt(name = "option", short = "O", number_of_values = 1)]
  compiler_options: Vec<String>,
  }
  