python3Packages.sounddevice: add cffi for cross compilation

Fixes

> ModuleNotFoundError: No module named '_cffi_backend'
>
> ERROR Backend subprocess exited when trying to invoke build_wheel

during the build.

pkgs/development/python-modules/sounddevice/default.nix

@@ -30,6 +30,8 @@ buildPythonPackage rec {
     portaudio
   ];
 
+  nativeBuildInputs = [ cffi ];
+
   # No tests included nor upstream available.
   doCheck = false;