code: function buildProject(timer, buildConf, buildManager) {
      let {logger, output: outputOpts} = buildConf;
      let {onBuildStart, onBuildDone} = buildConf.script || {};
  
      let hookResult = runBuildStartHook(buildManager, onBuildStart);
      let buildResult;
      if (hookResult instanceof Promise) {
          buildResult = hookResult.then(code => {
              logger.debug('init build start done...', code);
              return buildManager.build(timer);
          });
      }
      else {
          buildResult = buildManager.build(timer);
      }
  
      let doneHandler = buildDone.bind(null, timer, logger, outputOpts.dir);
      return buildResult.then(
          () => buildManager.release()
      ).then(
          doneHandler
      ).then(
          () => {
              runBuildDoneHook(buildManager, onBuildDone);
          }
      ).catch(doneHandler);
  }
docs: 构建
  
  @param {Object} timer         计时器实例
  @param {Object} buildConf     构建配置
  @param {Object} buildManager  构建实例
  @return {Promise}