Now I'm running in sandbox mode and it's not horrible broken. Nice!
> checking whether we are cross compiling... configure: error: in `/private/tmp/nix-build-racket-6.12.drv-0/racket-6.12/src/build':
> configure: error: cannot run C compiled programs.
> If you meant to cross compile, use `--host'.
> See `config.log' for more details
... never mind.