- gcc ships no supported switch to build libstdc++ with -fsanitize=thread,
and spack's gcc recipe filters all flags out of the target-library build
(CXXFLAGS_FOR_TARGET is owned by its generated --with-build-config=spack
makefile), so provide a dedicated libstdcxx-tsan package in a custom repo
- build only the libstdc++-v3 subtree from the matching gcc release tarball,
configured standalone against the already-installed toolchain (recipe
modeled on https://iree.dev/developers/debugging/sanitizers/), instead of
rebuilding all of gcc
- the result is a drop-in runtime replacement for the compiler's libstdc++
(same soname and symbol versions), to be loaded only by the instrumented
test executables
- normalize the install layout after make install: the standalone build puts
the runtime libraries into the multilib os dir (lib64 on x86_64) regardless
of --libdir, and --with-toolexeclibdir only applies to cross builds
- register the repo in the setup-deps action before creating the env
