Recently we upgraded to Gulp 4. However, the following things still need to be addressed in some way:

- If a task series is executed with an anonymous function inside it, we'll see `Starting '<anonymous>'` in the output, which isn't that great. We need to either suppress it or use named functions.
- If a task is private, it should be hidden in some way. For example, `gh-pages-prepare` is only used in the public `web` target and should not be used on its own, however currently it shows in the default `gulp` output since it's a regular task. Perhaps we should mark them with an underscore?
const plugins = [];
  if (!disableLicenseHeader) {
    plugins.push(
      new webpack2.BannerPlugin({ banner: licenseHeaderLibre, raw: true })
    );
  }
  
  output.globalObject = "this";
  return {
    mode: "none",
    output,
    performance: {
      hints: false, 
    },
    plugins,
    resolve: {
      alias: {
        pdfjs: path.join(__dirname, "src"),
        "pdfjs-web": path.join(__dirname, "web"),
        "pdfjs-lib": path.join(__dirname, "web/pdfjs"),
      },
    },
    devtool: enableSourceMaps ? "source-map" : undefined,
    module: {
      rules: [
        {
          loader: "babel-loader",
          exclude: babelExcludeRegExp,
          options: {
            presets: skipBabel ? undefined : ["@babel/preset-env"],