There is a report of unmet GL dep after libglvnd if it is built with OPTIONS_X11 unset, inside libGLU: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=241568#c4
It seems to me the correct way to handle this is to use the osmesa implementations for !X11This update was guided along by Matt Turner (gentoo/freedesktop) and makes libGLU not link to X11 when built with OPTIONS GLVND.