Make display manager and xfce optional during installation

[muhifauzan]

@demonkilleralg I'm really grateful for your work and I can't thank you enough for this distro option. There's something that bugs me and it's the display manager and the desktop that is installed by default. Is it possible so the user can choose between lightdm and sddm and make the xfce as optional instead of forced during the installation?

If it's not possible, may I ask you to teach me how to build an ISO image from your repo so I can make the adjustment and the ISO myself? I believe this is the commit where you introduced the new behaviour.