M1 Mac support

[srid]

The x86 version of Idris2 in nixpkgs is working, so we could use that in theory instead of doing native support. It would be great if the 'nix flake new' generated project worked seamlessly with it. Currently:

❯ nix flake new -t github:claymager/idris2-pkgs mypkg
...
❯ nix develop
warning: creating lock file '/private/tmp/mypkg/flake.lock'
error: flake 'path:/private/tmp/mypkg' does not provide attribute 'devShells.aarch64-darwin.devShell.aarch64-darwin', 'packages.aarch64-darwin.devShell.aarch64-darwin', 'legacyPackages.aarch64-darwin.devShell.aarch64-darwin', 'devShell.aarch64-darwin' or 'defaultPackage.aarch64-darwin'

and

❯ nix --system x86_64-darwin develop
error: a 'x86_64-darwin' with features {} is required to build '/nix/store/k174flg06xlgpmf8x0s2d7rfi2dd2ykn-idris2-0.5.1.drv', but I am a 'aarch64-darwin' with features {benchmark, big-parallel, nixos-test, recursive-nix}
(use '--show-trace' to show detailed location information)