code: function transpileAot() {
    // https://stackoverflow.com/questions/36897877/gulp-error-the-following-tasks-did-not-complete-did-you-forget-to-signal-async
    return new Promise(function(resolve, reject) {
      // Need to capture the exit code
      exec('node_modules/.bin/ngc -p tsconfig-aot.json', function (err, stdout, stderr) {
        console.log(stdout);
        console.log(stderr);
        if (err !== null) {
          process.exit(1);
        }
      });
      resolve();
    });
  }
docs: Build with AOT enabled