Grunt: async config using a wrapper task

Gruntfile.js

module.exports = function(grunt) {
  grunt.initConfig({});

  grunt.registerTask('require-wrapper', 'whatever', function() {
    var done = this.async();
    var args = this.args;
    // simulate async config building
    setTimeout(function() {
      // set config
      grunt.config('requirejs', {yay: true});
      // run "requirejs" task passing through all args after this task
      task.run('requirejs' + (args.length > 0 ? (':' + args.join(':')) : ''));
      // run next task
      done();
    }, 1000);
  });

};