win-virtio: deprecate phases

pkgs/applications/virtualization/driver/win-virtio/default.nix

···
   pname = "win-virtio";
   version = "0.1.196-1";
 
-  phases = [ "buildPhase" "installPhase" ];
+  dontUnpack = true;
 
   src = fetchurl {
     url = "https://fedorapeople.org/groups/virt/virtio-win/direct-downloads/archive-virtio/virtio-win-${version}/virtio-win.iso";