# Pastebin MR12oEn4
$ nix-build '<nixpkgs>' -A hello --argstr system x86_64-linux --show-trace --check
checking path(s) ‘/nix/store/qhnzr9ih4wk2k16q8g5sm56rldsyqxxv-hello-2.10’
error: a ‘x86_64-linux’ is required to build ‘/nix/store/ql6frh48fw1l7clqlpva9yxzn5ji8nwi-hello-2.10.drv’, but I am a ‘x86_64-darwin’