devel/llvm18: fix host dependent compiler output for i386

Merge fixes for a couple cases where the compiler generated different
i386 code depending on the host. In the base system this showed up as
very small differences in a couple object files in buildworld for i386
depending on the host architecture (i386 or amd64).

PR: 276961
(cherry picked from commit a4e0cb2fd99adef4cbd4f778be729a079a5f2dea)