fix: disable libcamera in pipewire for cross-compile (rpi-pisp blocks)

hosts/uconsole-cm5/configuration.nix

@@ -31,4 +31,11 @@
     enable = true;
     xwayland.enable = true;
   };
+
+  # Override pipewire to drop libcamera (fixes cross-compile: rpi-pisp subproject blocked)
+  nixpkgs.overlays = [
+    (final: prev: {
+      pipewire = prev.pipewire.override { libcamera = null; };
+    })
+  ];
 }