public function finalize(AssetTarget $build)
    {
        $ext = $build->ext();
        if (empty($this->timestamp[$ext])) {
            return;
        }
        $data = $this->_readTimestamp();
        $name = $this->buildCacheName($build);
        if (!isset($data[$name])) {
            return;
        }
        $time = $data[$name];
        unset($data[$name]);
        $this->_invalidated = null;
        $name = $this->buildCacheName($build);
        $data[$name] = $time;
        $this->_writeTimestamp($data);
    }