cmake: Add WITH_DBUS configuration option

[hebasto]

This PR adds a new WITH_DBUS configuration option, which is an analogue of Autotools' --with-qtdbus.

[fanquake]

Is this actually something we need (to port) an option for.

[hebasto]

Is this actually something we need (to port) an option for.

cc @laanwj

[laanwj]

Is this actually something we need (to port) an option for.

i think so. Not all UNIX platforms use DBUS. On Linux it's safe to assume it's there. On MacOS and Windows it's not a thing.

FWIW i tried to get rid of the custom notification stuff a while ago, but Qt's notificator still falls back to ancient X11 notifications which are ignored (or look very shitty) on modern Linux. Maybe qt6 changes this? i dunno. But for now t's really necessary.

[theuni]

Should probably get rid of the HAVE_CONFIG_H (in qt/notificator.cpp) ?

[hebasto]

Should probably get rid of the HAVE_CONFIG_H (in qt/notificator.cpp) ?

Sure. Removed.

[hebasto]

@theuni

Should probably get rid of the HAVE_CONFIG_H (in qt/notificator.cpp) ?

FWIW, #177 removes unsed HAVE_CONFIG_H in the entire codebase.

[hebasto]

Rebased.

[hebasto]

Rebased on top of the merged #173.

[sedited]

lgtm