app-emulation/vice-1.21 compiles and seems to be happy with gtk2, it doesn't need the gnome-base/libgnomeui which pulls whole gnome. The gnome useflag should be changed to e.g. gtk and the dependency to x11-libs/gtk+. I tried it and it seems to work (also with vice-1.22). Reproducible: Always
Please, read the configure.in file; it absolutely needs libgnomeui with USE=gnome (and that's exactly what the ebuild does).