fixed bug where required cuda packages could only be toggled through config.cudaSupport

Signed-off-by: Robbie Buxton <[e-mail]>

pkgs/development/libraries/dlib/default.nix

···
     lapack
   ]
   ++ lib.optionals guiSupport [ libX11 ]
-  ++ lib.optionals config.cudaSupport (with cudaPackages; [
+  ++ lib.optionals cudaSupport (with cudaPackages; [
     cuda_cudart.dev
     cuda_cudart.lib
     cuda_cudart.static