Without this, including sys/stddef.h after stddef.h can trigger aMove to sys/_offsetof.h and use __builtin_offsetof() instead of
warning which may become an error. This isn't something FreeBSD code__offsetof to avoid reintroducing sys/cdefs.h polution in stddef.h.
should do, but it does happen sometimes with compatibility headers so
This has the side effect of allowing sys/stddef.h to be included after
support it.stddef.h which can happen in compatability headers.
Effort: CHERI upstreaming
Sponsored by: DARPA, AFRL