- tsan build failed at link with GNU ld:
"failed to set dynamic section sizes: bad value" (known binutils +
ThreadSanitizer incompatibility); install lld and select it via
-fuse-ld=lld for the tsan job only
- pass -fuse-ld=lld through cxx-flags so it reaches the link line,
avoiding the semicolon-list pitfall of
list(APPEND CMAKE_EXE_LINKER_FLAGS ...)
- build the bundled googletest with CMAKE_POSITION_INDEPENDENT_CODE=ON:
lld rejects R_X86_64_32 relocations from the non-PIC libgtest.a when
producing the position-independent tsan executable; the bundle is built
by a separate cmake invocation, so the flag must be set there
