Nix shell to build CircuitPython on MacOS

shell.nix

{ pkgs ? import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/refs/tags/21.05.tar.gz") { }
, pkgs_x86_64 ? import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/refs/tags/21.05.tar.gz") { localSystem = "x86_64-darwin"; }
}:
with pkgs.python38Packages;
let
  cascadetoml = buildPythonPackage rec {
    pname = "cascadetoml";
    version = "0.3.0";

    src = fetchPypi {
      inherit pname version;
      sha256 = "1i2n54q80g1kn06a9y1bvi5gsl76mcazjqq93bmy9gpr6sqx13yy";
    };

    propagatedBuildInputs = [ parse tabulate tomlkit typer ];

    doCheck = false;
  };

  python = pkgs.python38.withPackages (
    ps: [ cascadetoml jinja2 ]
  );
in
pkgs.mkShell {
  buildInputs = with pkgs; [
    gettext
    git
    libffi
    pkgconfig
    pkgs_x86_64.gcc-arm-embedded
    python
  ];
}

Should be enough to build Cortex-M and Unix ports on x86_64 or aarch64 based Darwin systems.

eg:

$ nix-shell --pure
$ make -C mpy-cross
$ make -C ports/unix
$ make -C ports/atmel-samd BOARD=pyportal