新增于: v0.1.96
请求将打开文件描述符的所有数据刷新到存储设备。
具体实现是操作系统和设备特定的。
有关更多详细信息，请参考 POSIX fsync(2) 文档。
返回 undefined。
Added in: v0.1.96
Request that all data for the open file descriptor is flushed to the storage
device. The specific implementation is operating system and device specific.
Refer to the POSIX fsync(2) documentation for more detail. Returns undefined.