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/system/build.nix

@@ -0,0 +1,21 @@
+{ lib, ... }:
+let
+  inherit (lib) mkOption types;
+in
+{
+  options = {
+
+    system.build = mkOption {
+      default = {};
+      description = ''
+        Attribute set of derivations used to set up the system.
+      '';
+      type = types.submoduleWith {
+        modules = [{
+          freeformType = with types; lazyAttrsOf (uniq unspecified);
+        }];
+      };
+    };
+
+  };
+}