clean build dir contents only to support symlinking build dir

webpack.config.js

@@ -59,7 +59,7 @@ var options = {
   },
   plugins: [
     // clean the build folder
-    new CleanWebpackPlugin(["build"]),
+    new CleanWebpackPlugin(["build/*"]),
     // expose and write the allowed env vars on the compiled bundle
     new webpack.DefinePlugin({
       "process.env.NODE_ENV": JSON.stringify(env.NODE_ENV)