Does the upstream libffi work reliably on OSX by this time?
The bundled version of libffi was extracted from PyObjC, and that copy is itself a patched version of the system libffi on OSX. The reason I don't use the system libffi is both that I don't want to rely on older version of libffi, and because the system libffi causes crashes in PyObjC's testsuite (which contains a lot of edge cases).
I haven't looked into using the upstream version of libffi yet. PyObjC's version of libffi is a fairly old fork of upstream libffi where support for other systems was removed and support for darwin/x86 (and later darwin/x86-64) as added. The former at a time that the upstream libffi didn't support darwin/x86 at all (and at a time that darwin/x86 itself wasn't available on consumer devices).