Split PKGBUILD to have a desktop-installer and a standalone build

[fabiscafe]

With this, it will build 3 packages

• archinstall-gui-server
  The server that runs in the background and is needed to install

• archinstall-gui-standalone
  That's the (chromium based) full screen launcher, that was there before

• archinstall-gui-desktop
  is a menu entry that launches the default browser of the desktop and moves to http://127.0.0.1.

This split is important in cases people want to create an Archiso with desktop environment or a WM, where we don't need a full screen window or logic to start up X, but a menu entry.

It also comes with a nice Icon

It also uses git directly to get the sources, because I can't see a reason to not use it.

[Torxed]

I will have a quick test of this, just to make sure everything looks decent in testing.
But I really like this change. I haven't had time to spend on the GUI installer as the console based version has been getting ready to be imported to the official ISO. But I'll get right on this one! : )

[fabiscafe]

I haven't had time to spend on the GUI installer as the console based version has been getting ready to be imported to the official ISO.

No pressure 👍 and good to know that the console one is already at this level, wow!