uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

nixos/modules/virtualisation/qemu-guest-agent.nix

@@ -0,0 +1,45 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.qemuGuest;
+in {
+
+  options.services.qemuGuest = {
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+        description = "Whether to enable the qemu guest agent.";
+      };
+      package = mkOption {
+        type = types.package;
+        default = pkgs.qemu_kvm.ga;
+        defaultText = literalExpression "pkgs.qemu_kvm.ga";
+        description = "The QEMU guest agent package.";
+      };
+  };
+
+  config = mkIf cfg.enable (
+      mkMerge [
+    {
+
+      services.udev.extraRules = ''
+        SUBSYSTEM=="virtio-ports", ATTR{name}=="org.qemu.guest_agent.0", TAG+="systemd" ENV{SYSTEMD_WANTS}="qemu-guest-agent.service"
+      '';
+
+      systemd.services.qemu-guest-agent = {
+        description = "Run the QEMU Guest Agent";
+        serviceConfig = {
+          ExecStart = "${cfg.package}/bin/qemu-ga --statedir /run/qemu-ga";
+          Restart = "always";
+          RestartSec = 0;
+          # Runtime directory and mode
+          RuntimeDirectory = "qemu-ga";
+          RuntimeDirectoryMode = "0755";
+        };
+      };
+    }
+  ]
+  );
+}