kibana/packages/kbn-build/webpack.config.js

const path = require('path');

module.exports = {
  entry: {
    index: './src/index.js'
  },
  target: 'node',

  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: '[name].js',
    libraryTarget: 'commonjs2',
  },

  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /(node_modules)/,
        use: {
          loader: 'babel-loader'
        }
      },
      // Removing an unnecessary require from
      // https://github.com/ForbesLindesay/spawn-sync/blob/8ba6d1bd032917ff5f0cf68508b91bb628d16336/index.js#L3
      //
      // This require would cause warnings when building with Webpack, and it's
      // only required for Node <= 0.12.
      {
        test: /spawn-sync\/index\.js$/,
        use: {
          loader: 'string-replace-loader',
          options: {
            search: ` || require('./lib/spawn-sync')`,
            replace: '',
            strict: true
          }
        }
      }
    ]
  },

  node: {
    // Don't replace built-in globals
    __filename: false,
    __dirname: false
  }
};