Matthew Bauer 635b762569 systems: allow passing in string for cross/localSystem
This makes things a little bit more convenient. Just pass in like:

$ nix-build ’<nixpkgs>’ -A hello --argstr localSystem x86_64-linux --argstr crossSystem aarch64-linux
2019-06-04 11:17:25 -04:00
..
2019-04-30 12:59:38 -04:00
2019-04-23 21:48:57 -04:00
2019-04-23 21:48:57 -04:00