Include xdp-tools in the debugging comps group for AppStream variant.
    
    Only include it from x86_64 architecture.
    
    The kernel on non-x86_64 architectures lacks the features needed
    for xdp-tools.  Only include it for x86_64 to not ship a package
    that doesn't work on the other architectures
    
    Signed-off-by: Jan Kaluza <jkaluza@redhat.com>