[asan] Add an offset for the kernel address sanitizer on FreeBSD

This is based on a port of the sanitizer runtime to the FreeBSD kernel
that has been commited as https://cgit.freebsd.org/src/commit/?id=38da497a4dfcf1979c8c2b0e9f3fa0564035c147
and the following commits.

Reviewed By: emaste, dim
Differential Revision: https://reviews.llvm.org/D98285

GitOrigin-RevId: f511dc75e4c130abda77a30299402abaf04d8238
1 file changed