Achim Gratz wrote: [some nifty stuff with puzzlers in it...]
Unfortunately I can't help with the qt5 build questions. Been down that path and gotten lost. But if/when you have a package ready for test installation, I can shortly thereafter provide a patch to qt5-base that fixes the longstanding Cygwin-specific gnuplot vs qterminal issue. Upstream doesn't seem inclined to fix.
Regards, ..mark