The syntax-check rules are the one bit of make usage that will
stay around for a while after the meson conversion. Move them
into the build-aux directory in preparation for refactoring
to make them independent from automake.
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>