packaging: setup: adding an error message if no compatible CPUs are detected

With certain CPU models VMX support is not enought to support virtualization,
NX needs to be enabled too.
Adding an error message to explain it if no compatible CPUs are found.

Change-Id: Idfa1daa84a0168983d729f5ebed45e62054db4f9
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1103672
Signed-off-by: Simone Tiraboschi <stirabos@redhat.com>