Instantiating "host" CPU and querying it using qom-get has been the only
way of probing host CPU via QEMU until 2.9.0 implemented
query-cpu-model-expansion for x86_64. Even though libvirt never really
used the old way its result can be easily converted into the one
produced by query-cpu-model-expansion. Thus we can reuse the original
test data and possible get new data from hosts where QEMU does not
support the new QMP command.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

While "x86" is a CPU sub driver name, it is not a recognized name of any
architecture known to libvirt. Let's use "x86_64" prefix which can be
used with virArch APIs.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

We want to remove the file created by

    json <<<"$data" >$fname.json

in case it was empty.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

So far we only test CPUID -> CPU def conversion on artificial CPUID data
computed from another CPU def. This patch adds the infrastructure to
test this conversion on real data gathered from a host CPU and two
helper scripts for adding new test data:

- cpu-gather.sh runs cpuid tool and qemu-system-x86_64 to get CPUID data
  from the host CPU; this is what users can be asked to run if they run
  into an issue with host CPU detection in libvirt

- cpu-parse.sh takes the data generated by cpu-gather.sh and creates
  data files for CPU detection tests

The CPUID data queried from QEMU will eventually switch to the format
used by query-host-cpu QMP command once QEMU implements it. Until then
we just spawn QEMU with -cpu host and query the guest CPU in QOM. They
should both provide the same CPUID results, but query-host-cpu does not
require any guest CPU to be created by QEMU.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>