[sanitizer] Don't call dlerror() after swift_demangle lookup through dlsym

Because the call to `dlerror()` may actually want to print something, which turns into a deadlock
as showcased in #49223.

Instead rely on further call to dlsym to clear `dlerror` internal state if they
need to check the return status.

Differential Revision: https://reviews.llvm.org/D128992