You don't need MESSUI as QMC2 is a complete replacement for it other than in emulation menus or mouse clicks IDK exactly.
QMC2 development is very active with constant improvements happening everyday, so it's puzzling why people still spend time to make MESSUI function, when it was removed from the source for some rather obvious reasons that were stated by others.
You can find recent compiled builds posted on bannister forums. google "QMC2 - MAME/MESS Frontend"
If you wish to learn compiling your own I have a help thread there you can post in and I will assist you in doing that.