Swap #if blocks in uid.c so target platform gets checked before host

This avoids the case where a UEFI build on FreeBSD tries to call the system
issetugid function instead of returning 0 as it should do.

CLA: trivial

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/9158)