try crosspkgs as arg

Makefile

@@ -12,6 +12,7 @@ system: configuration.nix helios64.nix
 
 image: emmc-image.nix configuration.nix helios64.nix
 	nix-build '<nixpkgs/nixos>' \
+		--arg crossSystem '(import <nixpkgs> {}).lib.systems.examples.aarch64-multiplatform' \
 		--arg configuration ./emmc-image.nix \
 		-A config.system.build.sdImage \
 		-I nixpkgs=$(NIXPKGS) \

helios64.nix

@@ -1,12 +1,6 @@
-{ config, pkgs, lib, ... }:
-let
-#  crossPkgs = import pkgs.path { system = "x86_64-linux"; crossSystem = "aarch64-linux"; };
-  pkgs = import <nixpkgs> {
-    crossSystem = {
-      config = "aarch64-unknown-linux-gnu";
-    }; 
-  };
-in {
+{ pkgs, lib, ... }:
+
+{
   # Fan speed adjustment
   systemd.services.fans = {
     wantedBy = ["multi-user.target"];