This is very confusing as seen in #12974 or #12906. My suggestion would be "legacy."
"generic-es5",
  gulp.series(
    "buildnumber",
    "default_preferences",
    "locale",
    function scripting() {
      var defines = builder.merge(DEFINES, {
        GENERIC: true,
        SKIP_BABEL: false,
      });
      return createTemporaryScriptingBundle(defines);
    },
    function () {
      console.log();
      console.log("### Creating generic (ES5) viewer");
      var defines = builder.merge(DEFINES, {
        GENERIC: true,
        SKIP_BABEL: false,
      });
      return buildGeneric(defines, GENERIC_ES5_DIR);
    }
  )
);
function buildComponents(defines, dir) {
  rimraf.sync(dir);
  var COMPONENTS_IMAGES = [
    "web/images/annotation-*.svg",
    "web/images/loading-icon.gif",
    "web/images/shadow.png",
  ];