For each QEMU version there are usually several different,
architecture-dependedn scenarios that we're interested in testing;
however, since the test matrix has to be explicitly created by
calling DO_TEST_QEMU() multiple times with different arguments, we
end up with spotty coverage.

Fix this by implementing the arch-specific rules in code, which
result in the full coverage for a (version, arch) combo being
automatically achieved with a single call to DO_TEST_QEMU().

Unsurprisingly, this change results in a bunch of extra output
files being created.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NJiri Denemark <jdenemar@redhat.com>