Enable CONFIG_UBSAN and CONFIG_UBSAN_FATAL for the ARM64 and x86_64
build jobs, with debug enabled, which are later used for Xen tests on
QEMU and/or real hardware.
Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com> Reviewed-by: Michal Orzel <michal.orzel@amd.com> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com> R-Acked-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>