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 preprocessor2 = require("./external/builder/preprocessor2.js");
  const licenseHeader = fs.readFileSync("./src/license_header.js").toString();
  const ctx = {
    saveComments: false,
    defines,
  };
  return gulp.src("./src/pdf.sandbox.external.js").pipe(
    transform("utf8", content => {
      content = preprocessor2.preprocessPDFJSCode(ctx, content);
      return `${licenseHeader}\n${content}`;
    })
  );
}
function createTemporaryScriptingBundle(defines, extraOptions = undefined) {
  return createScriptingBundle(defines, {
    disableVersionInfo: !!(extraOptions && extraOptions.disableVersionInfo),
    disableSourceMaps: true,
    disableLicenseHeader: true,
  }).pipe(gulp.dest(TMP_DIR));
}
function createSandboxBundle(defines, extraOptions = undefined) {