Fix filtering noarch RPMs
    
    The list of arches we compare against should not include multilib
    arches. Otherwise excluding does not behave correctly.
    
    Example:
    A build has ExcludeArch: i686 (because it only works on 64 bit arches).
    A noarch package is built there, but it would be excluded from x86_64.
    
    Relates: https://pagure.io/pungi/pull-request/1050
    Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>