[llvm] [FreeBSD] Mark __stack_chk_guard dso_local except for PPC64 (PR #86665)

[Fangrui Song via llvm-commits]

https://github.com/MaskRay approved this pull request.

We should have a powerpc64 freebsd test as well, if we haven't yet.

https://github.com/llvm/llvm-project/pull/86665