Stack/Nix: Updated doc to reflect expected behaviour of buildStackProject
Stack/Nix: Updated doc to reflect expected behaviour of buildStackProject

See https://github.com/NixOS/nixpkgs/pull/15989

deech/stack,MichielDerhaeg/stack,Blaisorblade/stack,anton-dessiatov/stack,Fuuzetsu/stack,martin-kolinek/stack,AndreasPK/stack,AndreasPK/stack,sjakobi/stack,Blaisorblade/stack,sjakobi/stack,AndrewRademacher/stack,anton-dessiatov/stack,juhp/stack,deech/stack,mrkkrp/stack,mrkkrp/stack,juhp/stack,MichielDerhaeg/stack,martin-kolinek/stack,AndrewRademacher/stack,Fuuzetsu/stack