[Ember] Ember serve or Ember build

As most of us know that we can invoke ember s to run ember application.

Steps are ember serve will trigger ember build to build the application to dist (default) directory first, then run express server to server ember application.

See code: https://github.com/ember-cli/ember-cli/blob/6ec50a1fd21d961f0b0e2ca4daf66a8e7dea6417/lib/tasks/serve.js#L41

It checks local server exists or not by `existsSync`, if it exists, local server will override ember’s default behavior. One can generate server by running `ember g server`, and delete server by `rm server`

I guess such option does not exist to override `ember build`, since In https://github.com/ember-cli/ember-cli/blob/master/lib/tasks/build.js, it does not check existence of such build file.

Also worthy knowing that, since build does not care about ./server directory, server directory will be ignore and not effect anything when run `ember build`.

One clap, two clap, three clap, forty?

By clapping more or less, you can signal to us which stories really stand out.