clang: stop linking _p libs for -pg as of FreeBSD 14

In FreeBSD 14 we will stop providing _p libraries (compiled with -pg).

[Note this is controlled by the target version. There is no change for
FreeBSD <= 13.]

Reviewed by: dim (upstream)
Obtained from: LLVM 699d47472c3f
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D30861

(cherry picked from commit b762974cf4b9ea77f1decf4a6d829372f0a97f75)