title: Error LicenseWebpackPlugin is not a constructor with Angular CLI
body: <p>I need help. I have a project in angular 4 with angular cli 1.4.5. When I execute "ng build" all works fine, but when I execute "ng build --prod" get an error:</p>
  
  <pre><code>license_webpack_plugin_1.LicenseWebpackPlugin is not a constructor
  TypeError: license_webpack_plugin_1.LicenseWebpackPlugin is not a constructor
      at Object.getProdConfig (D:\Proyectos\Angular\project-name\node_modules\@angular\cli\models\webpack-configs\produ
  ction.js:81:27)
      at NgCliWebpackConfig.getTargetConfig (D:\Proyectos\Angular\project-name\node_modules\@angular\cli\models\webpack
  -config.js:40:42)
      at NgCliWebpackConfig.buildConfig (D:\Proyectos\Angular\project-name\node_modules\@angular\cli\models\webpack-con
  fig.js:24:18)
      at Class.run (D:\Proyectos\Angular\project-name\node_modules\@angular\cli\tasks\build.js:27:92)
      at Class.run (D:\Proyectos\Angular\project-name\node_modules\@angular\cli\commands\build.js:204:26)
      at resolve (D:\Proyectos\Angular\project-name\node_modules\@angular\cli\ember-cli\lib\models\command.js:261:20)
      at Promise (&lt;anonymous&gt;)
      at Class.validateAndRun (D:\Proyectos\Angular\project-name\node_modules\@angular\cli\ember-cli\lib\models\command
  .js:240:12)
      at Promise.resolve.then.then (D:\Proyectos\Angular\project-name\node_modules\@angular\cli\ember-cli\lib\cli\cli.j
  s:140:24)
      at &lt;anonymous&gt;
  </code></pre>
  
  <p>I hope your help, please.</p>