title: Angular - Configuration is not set in the workspace
body: <p>I try to serve my Angular app with my specific configuration but Angular does not recognize it : </p>
  
  <pre class="lang-sh prettyprint-override"><code>$ ng serve --configuration=fr
  An unhandled exception occurred: Configuration 'fr' is not set in the workspace.
  See "/tmp/ng-nyZPjp/angular-errors.log" for further details.
  </code></pre>
  
  <p>My angular.json : </p>
  
  <pre><code>"configurations": {
    "fr": {
      "aot": true,
      "outputPath": "dist/fr/",
      "i18nFile": "src/i18n/messages.fr.xlf",
      "i18nFormat": "xlf",
      "i18nLocale": "fr",
      "i18nMissingTranslation": "error",
      "baseHref": "/fr/"
    },
    "en": { 
      "aot": true,
      "outputPath": "dist/en/",
      "i18nFile": "src/i18n/messages.en.xlf",
      "i18nFormat": "xlf",
      "i18nLocale": "en",
      "i18nMissingTranslation": "error",
      "baseHref": "/en/"
    },
      ...
  </code></pre>
  
  <p><code>ng serve --configuration=en</code> works perfectly</p>