Check whether with_debug is defined
    
    We want to check whether with_debug is defined, and if so set the
    appropriate "_find_debuginfo_dwz_opts" and "_dwz_low_mem_die_limit"
    values.
    
    The way it's done nowadays seems like a typo when adding the
    conditional / conditional expansion, as it's missing a "?".
    
    Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>