Reduce flash initrd sizes

[jmbaur]

Description of changes

By reusing shared libraries across all dependencies of the initrd used in flashing the platform firmware, we can reduce the size of the initrd ~20MiB.

Testing

Tested initrd flashing on an orin-agx-devkit and xavier-agx-devkit with success.

Sizes compared with the following:

# nix run -L -f <this-file>

let
  jetpack-nixos-master = builtins.getFlake "github:anduril/jetpack-nixos";
  jetpack-nixos-flash-initrd-min = builtins.getFlake "github:jmbaur/jetpack-nixos/flash-initrd-reduce-size";
  nixpkgs = builtins.getFlake "github:nixos/nixpkgs/nixos-unstable";

  nixosSystem =
    jetpack-nixos:
    nixpkgs.lib.nixosSystem {
      modules = [
        jetpack-nixos.nixosModules.default
        {
          nixpkgs.buildPlatform = builtins.currentSystem;
          boot.loader.grub.enable = false;
          hardware.nvidia-jetpack = {
            enable = true;
            som = "orin-agx";
            carrierBoard = "devkit";
          };
        }
      ];
    };
in
(import nixpkgs { system = builtins.currentSystem; }).callPackage (
  { writeShellScriptBin }:
  writeShellScriptBin "compare" ''
    echo master: $(du -h ${(nixosSystem jetpack-nixos-master)._module.args.pkgs.nvidia-jetpack.flashInitrd}/initrd)
    echo here: $(du -h ${(nixosSystem jetpack-nixos-flash-initrd-min)._module.args.pkgs.nvidia-jetpack.flashInitrd}/initrd)
  ''
) { }

[danielfullmer]

Closing in favor of #281. Thanks for noticing though!