They are intended to be used by other objects than the master clock, so don't keep the declaration there. https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1285
In cogl use cogl-config.h and in clutter use clutter-build-config.h. We can't use clutter-config.h in clutter because its already used and installed. https://bugzilla.gnome.org/show_bug.cgi?id=768976
