Add kexec-bundle package to flake

flake.nix

@@ -169,6 +169,23 @@
 
           });
 
+        packages = {
+          kexec-bundle = (nixpkgs.lib.nixosSystem {
+            inherit system;
+
+            modules = [
+              ./modules/pubkeys.nix
+              ./modules/ssh.nix
+
+              ({ modulesPath, ... }: {
+                imports = [
+                  (modulesPath + "/installer/netboot/netboot-minimal.nix")
+                ];
+              })
+            ];
+          }).config.system.build.kexecTree;
+        };
+
         devShells.default = pkgs.mkShell {
           buildInputs = (with pkgs; [
             black