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 GLOBALS = "/* eslint-disable */\n";
  const MODIFICATION_WARNING =
    "//\n// THIS FILE IS GENERATED AUTOMATICALLY, DO NOT EDIT MANUALLY!\n//\n";
  const bundleDefines = builder.merge(DEFINES, {
    DEFAULT_PREFERENCES: getDefaultPreferences("mozcentral/"),
  });
  content = preprocessor2.preprocessPDFJSCode(
    {
      rootPath: __dirname,
      defines: bundleDefines,
    },
    content
  );
  return (
    licenseHeader +
    "\n" +
    GLOBALS +
    "\n" +
    MODIFICATION_WARNING +
    "\n" +
    content +
    "\n"
  );
}
gulp.task(
  "mozcentral-pre",