Remove the bare Linux libtsan lookup that mixes GCC's shared runtime with
Clang's instrumented host. Add an ELF linkage test that requires actual
TSan instrumentation and rejects the other compiler's runtime.
Include cstring explicitly for retrieval-session memory operations.
The regression was exercised against the actual instrumented shared object;
no sanitizer instrumentation, interceptors, or checks are disabled.
Signed-off-by: trvon <git@trevon.dev>
