修改如下：

module.exports = {
  // ... many config ...
  productionSourceMap: process.env.NODE_ENV === 'development',
  // ... many config ...
  configureWebpack: {
    devtool: process.env.NODE_ENV === 'development' ? 'source-map' : undefined,
    // ... many config ...
  }
}

另：上述的development要看你本地配置，有的是dev