GUI only takes values UNX or WNT, so it is fairly pointless. One can check
whether OS is WNT or not instead.

Change-Id: I78ae32c03536a496a563e5deeb0fca78aebf9c34
Reviewed-on: https://gerrit.libreoffice.org/1304Reviewed-by: Peter Foley <pefoley2@verizon.net>
Tested-by: Peter Foley <pefoley2@verizon.net>