Borked systems (mine, for example). :-) I don't know why, but I could
not compile Chicken with libffi on my machine. I may be wrong, but
I'm pretty sure it's a local problem, since I could build it fine on
another system. Anyway, using configure's --without-libffi I could at
least have a running Chicken.
If the system can work fine, but is currently borked, then you should fix
it. This is true for any build environment on any system.
If all such systems are borked, then if you can define the borking, we can
put some system-specific IF(bork) code in there.
If you want a quick 'n' dirty hack for your personal use, just go into
CMakeLists.txt and comment out the ffi.h stuff. But I don't see a reason to
support that kind of operation with a special build flag. Rather, I think
you should find out why it's borked, so we can do what should be done.