code: function buildFirebaseUiJs(locale) {
    const flags = {
      closure_entry_point: 'firebaseui.auth.exports',
      define: `goog.LOCALE='${locale}'`,
      externs: [
        'node_modules/firebase/externs/firebase-app-externs.js',
        'node_modules/firebase/externs/firebase-auth-externs.js',
        'node_modules/firebase/externs/firebase-client-auth-externs.js'
      ],
      only_closure_dependencies: true,
      output_wrapper: OUTPUT_WRAPPER,
  
      // This is required to match XTB IDs to the JS/Soy messages.
      translations_project: 'FirebaseUI'
    };
    if (locale !== DEFAULT_LOCALE) {
      flags.translations_file = `translations/${locale}.xtb`;
    }
    return compile([
      'node_modules/google-closure-templates/javascript/soyutils_usegoog.js',
      'node_modules/google-closure-library/closure/goog/**/*.js',
      'node_modules/google-closure-library/third_party/closure/goog/**/*.js',
      `${TMP_DIR}/**/*.js`,
      'javascript/**/*.js'
    ], getTmpJsPath(locale), flags);
  }
docs: Builds the core FirebaseUI binary in the given locale.
  @param {string} locale
  @return {*} A stream that finishes when compilation finishes.