automation: Build Xen according to the type of the job

automation: Build Xen according to the type of the job

All the build jobs exist in two flavors: debug and non-debug, where the
former sets 'debug' variable to 'y' and the latter to 'n'. This variable
is only being recognized by the toolstack, because Xen requires
enabling/disabling debug build via e.g. menuconfig/config file.
As a corollary, we end up building/testing Xen with CONFIG_DEBUG always
set to a default value ('y' for unstable and 'n' for stable branches),
regardless of the type of the build job.

Fix this behavior by setting CONFIG_DEBUG according to the 'debug' value.

Signed-off-by: Michal Orzel <michal.orzel@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>