Re: [RFC QEMU PATCH] ui: Make the DisplayType enum entries conditional

Libvirt's "domcapabilities" command has a way to state whether certain graphic frontends are available in QEMU or not. Originally, libvirt looked at the "--help" output of the QEMU binary to determine whether SDL was available or not (by looking for the "-sdl" parameter in the help text), but since libvirt stopped doing this analysis of the help text, the detection of SDL is currently broken, see: https://bugzilla.redhat.com/show_bug.cgi?id=1790902 QEMU should provide a way via the QMP interface instead. The simplest way, without introducing additional commands, is to make the DisplayType enum entries conditional, so that the enum only contains the entries if the corresponding CONFIG_xxx switches have been set.