bootstrap = async argv => {
  // globalSetup and globalTeardown do not run in workers
  const plugins = await handleRequires(argv.require, {
    ignoredPlugins: ['mochaGlobalSetup', 'mochaGlobalTeardown']
  });
  validateLegacyPlugin(argv, 'ui', Mocha.interfaces);

  rootHooks = plugins.rootHooks;
  bootstrap = () => {};
  debug('bootstrap(): finished with args: %O', argv);
}
Initializes some stuff on the first call to {@link run}.

Handles `--require` and `--ui`.  Does _not_ handle `--reporter`,
as only the `Buffered` reporter is used.

**This function only runs once per worker**; it overwrites itself with a no-op
before returning.

@param {Options} argv - Command-line options