to auto-substitued the libs and headers.
o unconditionally build qfcc (for now, anyway) when building quakeforge
(needed for cs-code compilation)
o when built as part of quakeforge (qfcc should still be buildable
independently) always enable cpp
o autoconfiscate the client-side code
o build the client-side code using the built qfcc
o install the client-side code in $(datadir)/quakeforge/id1