`ember s --prod` does not update hash between rebuilds.

The hash of files are not update between rebuilds when running the Ember CLI server in production mode.

Background: I'm caching the asset with a service worker. Ember CLI SRI does update the integrity hash between rebuilds, this causes the changed asset to not load.

-----

To reproduce:

```
ember new test-app
cd test-app
ember s --prod
```

Now open `localhost:4200` and note down the hash of `test-app.js`.

```
ember g component foo-bar
```

App reloads, note that the hash of `test-app.js` is still the same.

Now kill the test server and serve again with `ember s --prod`. Now the hash of `test-app.js` did change.