NVIDIA drivers have a vendor of "NVIDIA Corporation" not "NVIDIA". Check for both in case older drivers did use "NVIDIA" https://bugzilla.gnome.org/show_bug.cgi?id=779039
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