The current condition `stdenv.hostPlatform == "x86_64-linux"` will never be true, because `stdenv.hostPlatform` is not a string. The intent is to use `rocmPackages.clr` only where clang-rocm can run, which is only on x86_64-linux. We can't use `lib.meta.availableOn` for `rocmPackages.clr` because it only checks `meta.platform` for the package, but not for its transitive dependencies that are unavailable.