gnuwin includes version 1.0.9 of libxslt. However xsltproc.exe fails to start.
Solution is to get latest files from here:
and install these files manually in the gnuwin32 folders.
Note: This issue was reported here (https://sourceforge.net/projects/gnuwin32/forums/forum/131144/topic/2706083) but it doesn't look like a bug was filed.