On OpenBSD, USE_FFI_CLOSURE_ALLOC was always set to 0 previously. In
633a1f15d8, the code was modified in a
way that it ended up being set to 1 on OpenBSD. However, that results
in SIGABRT when running make test-all, inside ffi_closure_free.
Setting USE_FFI_CLOSURE_ALLOC back to 0 fixes the issue.