my_write() sets inappropriate errno, if WriteFile fails with ERROR_FILE_SYSTEM_LIMITATION

WriteFile may fail if number of NTFS extents reached limit. GetLastError() returns 665 (ERROR_FILE_SYSTEM_LIMITATION), and this is mapped to catch-all generic EINVAL,
which does not help much with troubleshooting.

In one case , as reported by support, mariabackup was returning EINVAL during write of a large file, and it required procmon tracing to find out the actual reason for failure.