How do you build Rebol's "Ren-C" branch with LibFFI support?
<p>I'd like to access a dynamic library using FFI features in the <a href="https://github.com/metaeducation/ren-c" rel="nofollow">Ren-C</a> Rebol branch. I understand this is possible by building with LibFFI support enabled. What steps do I need to take to enable this?</p>

<p>I mainly use OS X for development, though would also like to be able to build it for use with Linux.</p>