qt5-build is only for building Qt itself. doomsday is now broken because of changes in that eclass that are not intended for non-dev-qt packages: games-fps/doomsday/doomsday-1.15.7.ebuild: DEPEND: ~amd64(default/linux/amd64/13.0) ['~dev-qt/qttest-1.15.7']
wow, I'm amazed it worked at all.