powerdevil: add DDC support

pkgs/desktops/plasma-5/powerdevil.nix

@@ -3,7 +3,7 @@
   extra-cmake-modules, kdoctools,
   bluez-qt, kactivities, kauth, kconfig, kdbusaddons, kdelibs4support,
   kglobalaccel, ki18n, kidletime, kio, knotifyconfig, kwayland, libkscreen,
-  networkmanager-qt, plasma-workspace, qtx11extras, solid, udev
+  ddcutil, networkmanager-qt, plasma-workspace, qtx11extras, solid, udev
 }:
 
 mkDerivation {
@@ -13,5 +13,9 @@ mkDerivation {
     kconfig kdbusaddons knotifyconfig solid udev bluez-qt kactivities kauth
     kdelibs4support kglobalaccel ki18n kio kidletime kwayland libkscreen
     networkmanager-qt plasma-workspace qtx11extras
+    ddcutil
+  ];
+  cmakeFlags = [
+    "-DHAVE_DDCUTIL=On"
   ];
 }