This capability can be used to figure out whether the
QEMU binary at hand supports the machine type property
we need in order to enable SMMUv3 IOMMU support.

Unfortunately we can't avoid probing the RISC-V binaries
along with the ARM ones, since both architectures have
their own 'virt' machine type.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>