Fix building rescue/rescue when sanitizers are enabled

We have to ensure that we don't link any instrumented object files
into rescue as it is a static executable and static binaries can't
use the sanitizer runtime.

Reviewed By: imp
Differential Revision: https://reviews.freebsd.org/D31044

(cherry picked from commit 2eefc1d926430dbba83128d27f8bed3c34199159)