Since libxfce4menu only depends on glib, doesn't link with gtk2, and gtk2 is only needed to build the regress tests, it seems to me that libxfce4menu-0.1.pc:Requires: gtk+-2.0 is wrong.
Fixed in revision 29728: * libxfce4menu/libxfce4menu-0.1.pc.in: Remove gtk+-2.0 from the dependency field. Add glib-2.0 and gthread-2.0 instead.