lib/systems: disable pipewireSupport in qemu-user

Option added in 5b0ed68c10

it causes infinite recursion in cross builds

There's a another inf rec that needs 6946977de0 which is in staging

lib/systems/default.nix

@@ -224,6 +224,7 @@ rec {
               gtkSupport = false;
               sdlSupport = false;
               pulseSupport = false;
+              pipewireSupport = false;
               smbdSupport = false;
               seccompSupport = false;
               enableDocs = false;