message: Use `fs` library so even Windows users can run build.
diff: 'use strict'
  process.env.NODE_ENV = 'production'
  -const exec = require('child_process').execSync
  const webpack = require('webpack')
  const ExtractTextPlugin = require('extract-text-webpack-plugin')
  const ProgressPlugin = require('webpack/lib/ProgressPlugin')
  // const OfflinePlugin = require('offline-plugin')
  const base = require('./webpack.base')
  const config = require('./config')
  +const fs = require('fs')
  +const distFolder = 'dist/';
  -exec('rm -rf dist/')
  +if (fs.existsSync(distFolder))
  + fs.rmdirSync(distFolder)
  +
  base.devtool = 'cheap-source-map'
  base.module.loaders.push(
  {
  