message: Fix sendfile in MACOS.
diff: int swoole_sendfile(int out_fd, int in_fd, off_t *offset, size_t size)
  {
  - off_t sent_bytes = 0;
  int ret;
  #ifdef __MACH__
  @@ -47,18 +46,13 @@ int swoole_sendfile(int out_fd, int in_fd, off_t *offset, size_t size)
  *offset += size;
  if (ret == -1)
  {
  - if (errno == EAGAIN)
  - {
  - *offset += sent_bytes;
  - return sent_bytes;
  - }
  - else if (errno == EINTR)
  + if (errno == EINTR)
  {
  goto do_sendfile;
  }
  else
  {
  - return SW_ERR;
  + return ret;
  }
  }
  else if (ret == 0)
  