installer: enable vmware guest support on x86 only

The vmware guest module asserts on this exact condition, so let's only
enable it on that condition.

nixos/modules/installer/cd-dvd/installation-cd-graphical-base.nix

@@ -38,7 +38,7 @@ with lib;
   # VM guest additions to improve host-guest interaction
   services.spice-vdagentd.enable = true;
   services.qemuGuest.enable = true;
-  virtualisation.vmware.guest.enable = true;
+  virtualisation.vmware.guest.enable = pkgs.stdenv.hostPlatform.isx86;
   virtualisation.hypervGuest.enable = true;
   services.xe-guest-utilities.enable = true;
   # The VirtualBox guest additions rely on an out-of-tree kernel module