The cogl/clutter merge made the .gitignore files in the respective directories incorrect, due to the using absolute paths. https://bugzilla.gnome.org/show_bug.cgi?id=768976
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