initrd cannot be cross-compiled due to pkgs.writeShellScriptBin usage

[delroth]

Issue description

The current implementation of pkgs.writeShellScriptBin generates a shell script to be executed on the target, not the host. Looking through most of the usage in nixpkgs, it all seems fine except for the call site in nixos/modules/system/boot/stage-1.nix

I have a local patch replacing it in stage-1.nix with pkgs.writeTextFile { executable = true; ... } but I'm not sure if there's a better solution for this.

@matthewbauer @illegalprime relevant to your interests, maybe.

Steps to reproduce

Try to cross-compile a NixOS initrd.