title: How to set environment via `ng serve` in Angular 6
body: <p>I am trying to update my Angular 5.2 app to Angular 6. I successfully followed instructions in the Angular update guide (including the update of <code>angular-cli</code> to v6), and now I am trying to serve the app via</p>
  
  <pre><code>ng serve --env=local
  </code></pre>
  
  <p>But this gives me error:</p>
  
  <blockquote>
    <p>Unknown option: '--env'</p>
  </blockquote>
  
  <p>I use multiple environments (<code>dev/local/prod</code>), and this is the way it was working in Angular 5.2. How can I set the environment now in Angular 6?</p>