This is very confusing as seen in #12974 or #12906. My suggestion would be "legacy."
var preprocessor2 = require("./external/builder/preprocessor2.js");
  var licenseHeader = fs.readFileSync("./src/license_header.js").toString();
  var GLOBALS = "/* eslint-disable */\n";
  var MODIFICATION_WARNING =
    "//\n// THIS FILE IS GENERATED AUTOMATICALLY, DO NOT EDIT MANUALLY!\n//\n";
  content = preprocessor2.preprocessPDFJSCode(
    {
      rootPath: __dirname,
      defines: DEFINES,
    },
    content
  );
  return (
    licenseHeader +
    "\n" +
    GLOBALS +
    "\n" +
    MODIFICATION_WARNING +
    "\n" +
    content +
    "\n"