ArmVirtPkg/PlatformCI: Add CI coverage for ArmVirtQemuKernel

ArmVirtPkg/PlatformCI: Add CI coverage for ArmVirtQemuKernel

ArmVirtQemuKernel.dsc describes a firmware build that is loadable at
arbitrary address and can be invoked using the Linux/arm64 kernel boot
protocol. The early code deviates significantly from ArmVirtQemu, and so
it makes sense to cover this platform in CI even if it is not widely
used. This ensures that the relocatable PrePi and other components in
EmbeddedPkg don't regress on ARM as they are being updated for use on
TDVF.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Michael Kubacki <michael.kubacki@microsoft.com>