Write webpack config to /tmp

temp.js

return {
  // ...
  plugins: [
    // ...
    {
      apply(compiler) {
        compiler.hooks.beforeRun.tapAsync("WebpackConfig", function(compiler, cb) {
          require("fs").writeFileSync("/tmp/webpack.config.new.js", require('util').inspect(compiler.options, {depth: 6, compact: false, sorted: true}), "utf8");
          cb();
        });
      }
    }
  ]
}