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

Adjust logic of 1cb9f37a to match freebsd/freebsd-src@9a4d48a645a7a.

D113443 is the original attempt to bring this FreeBSD patch to
llvm-project,
but it never landed. This change is required to build FreeBSD kernel
modules
with -fstack-protector using a standard LLVM toolchain. The FreeBSD
kernel
loader does not handle R_X86_64_REX_GOTPCRELX relocations.

Fixes #50932.