Can you retry it with the latest source from github?  It /should/
build both with and without libffi installed from ports.  If it isn't
installed, it should use the in-tree version.

2010/1/13 bmo <brianmo@yahoo.com>:

> Just a FYI, this is an encapsulation of a email thread from a month
> ago or so -- if you're missing ffi.h when installing on 10.5.8, you
> should
>
> port install libffi
>
> An even better non-workaround would be to change extconf.rb in the ffi
> gem to actually build libffi (which is included in the ext/ffi_c/
> libffi directory), and modify the include and link paths in the
> Makefile accordingly if ffi.h isn't originally found.
>
> Brian Moran
> http://www.onehub.com
>