https://bugs.winehq.org/show_bug.cgi?id=31910
--- Comment #21 from Robert Walker bob.mt.wya@gmail.com --- (In reply to Jan Havran from comment #20) ...
The lowest log size after xz -z compression is 5715 KiB (attachment limit is 5000)
...
You want:
xz -9 -e
to get maximum log file compression...