title: remove duplicate sass imports (webpack)
body: <p>I have a big project with a lot of sass files (and all of them import a main sass file with some varibales and classes).</p>
  
  <p>I belive you all know the problem that the file that i am import in all of my css files is duplicate in the main css file after buiding the project.</p>
  
  <p>i tried using ExtractTextPlugin options and plugin that called OptimizeCssAssetsPlugin, and i didnt find solution for this problem.</p>
  
  <p>Here is the plugins array in my webpack prod config:</p>
  
  <pre><code>new ExtractTextPlugin({
            filename: "styles.css",
        }),
        new OptimizeCssAssetsPlugin({
            assetNameRegExp: /\.optimize\.css$/g,
            cssProcessor: require('cssnano'),
            cssProcessorOptions: { safe: true, discardComments: { removeAll: true } },
            canPrint: true
        }),
  </code></pre>
  
  <p>anyone know the solution for this problem? </p>
  
  <p>thank you!</p>