Update ffi gem to v1.17.0

ffi v1.15.5 does not appear to compile on macOS with clang 16.0 at the
moment. Update to ffi v1.17.0 to fix this, but don't use the
newly-introduced precompiled gems because Omnibus needs to compile
this in order to get the right default LD_LIBRARY_PATH.

Omnibus GitLab has already been using ffi v1.17.0 since GitLab 17.1
(https://gitlab.com/gitlab-org/omnibus-gitlab/-/merge_requests/7670).

Diff: https://my.diffend.io/gems/ffi/1.16.3/1.17.0

Changelog: changed