In most products dom0 used as a control domain and
not as backend domain.

Signed-off-by: Andrii Chepurnyi <[email protected]>

In our configuration, QEMU uses libsdl2 as a backend for display.
At the same time, in weston build, libsdl2 uses weston window for
display output. In non weston build it is proposed to use drmkms
for the display output.

Signed-off-by: Andrii Chepurnyi <[email protected]>

Introduce new property XT_DOMD_DISPLAY_SYSTEM, which will hint
display system in DomD to chose appropriate domain dependancies for start.
I.e. if weston used - we assume that prior guest start, weston should be
ready and running to give possibility for gues draw into window.

Signed-off-by: Andrii Chepurnyi <[email protected]>