libftdi: do not force a build of python if !pythonSupport

libftdi has a `pythonSupport` parameter, but still produces a
(build-time) dependency on python even when it is set to `false`.
This commit corrects that.

This allows building tiny systems (think embedded widgets) that need
libftdi, without having to cross-build all of python for the target
system.

pkgs/development/libraries/libftdi/1.x.nix

@@ -44,6 +44,7 @@ stdenv.mkDerivation rec {
     "-DLINK_PYTHON_LIBRARY=${onOff pythonSupport}"
     "-DPYTHON_BINDINGS=${onOff pythonSupport}"
     "-DDOCUMENTATION=${onOff docSupport}"
+  ] ++ lib.optionals pythonSupport [
     "-DPYTHON_EXECUTABLE=${python3.pythonForBuild.interpreter}"
     "-DPYTHON_LIBRARY=${python3}/lib/libpython${python3.pythonVersion}${stdenv.hostPlatform.extensions.sharedLibrary}"
   ];