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
Clutter out of tree depends on Cogl's required dependencies via the
pkg-config file. Since Clutter and Cogl moved in tree, it means that
those dependencies need to be checked by Clutter itself, otherwise
headers and libraries won't be found.
