ember-cli-build.js | set broccoli's params deppending of environmnet

I tried to search in google this but without the correct answer if I need to do.

Its a simple question I have my ember-cli-build.js

  /*jshint node:true*/
  /* global require, module */
  var EmberApp = require('ember-cli/lib/broccoli/ember-app');

  module.exports = function(defaults) {
    var app = new EmberApp(defaults, {
      storeConfigInMeta: false,
      minifyJS: {
        enabled: false
      },
      minifyCSS: {
        enabled: false
      }
    });


    return app.toTree();
  };

And I want change the value of minifyJS or minifyCSS deppending if I am running ember in production or dev, how can achieve that ??