title: How to specify cacheDirectory option when using babel-loader with webpack?
body: <p>There is a <a href="https://github.com/babel/babel-loader#options">cacheDirectory</a> option in babel-loader. I can't figure out how to use it with the following webpack setup:</p>
  
  <pre><code>var compiler = webpack( {
      context: path.resolve( __dirname + "/../../" + rootModuleDir + "/" + modules[ module ] ),
      entry: "./index.jsx",
      resolve: {
          root: path.resolve( __dirname + "/../../assets/js/lib/react" ),
          extensions: [ "", ".js", ".jsx" ]
      },
      output: {
          path: targetDir,
          filename: modules[ module ] + ".js"
      },
      module: {
          loaders: [
              { test: /\.jsx?$/, exclude: /node_modules/, loader: "babel-loader?optional=runtime" }
          ]
      },
      plugins: [
          //new webpack.optimize.UglifyJsPlugin(),
          new webpack.SourceMapDevToolPlugin( {
              filename: "[file].map"
          } )
      ]
  } );
  </code></pre>
  
  <p>Where should it go?</p>