See https://nix.dev/tutorials/cross-compilation.html

and

https://github.com/NixOS/nixpkgs/blob/07b889196841399386c384461586b52901b68439/pkgs/build-support/docker/examples.nix#L580

  # basic example, with cross compilation
  cross = let
    # Cross compile for x86_64 if on aarch64
    crossPkgs =
      if pkgs.stdenv.hostPlatform.system == "aarch64-linux" then pkgsCross.gnu64
      else pkgsCross.aarch64-multiplatform;
  in crossPkgs.dockerTools.buildImage {
    name = "hello-cross";
    tag = "latest";
    copyToRoot = pkgs.buildEnv {
      name = "image-root";
      pathsToLink = [ "/bin" ];
      paths = [ crossPkgs.hello ];
    };
  };