fixup export-libs macro logic
    
       1 /sbin/ldconfig: relative path `1' used to build cache
       2 warning: %postun(bind-export-libs-32:9.11.4-6.P1.fc29.x86_64) scriptlet failed, exit status 1
    
    The reason for that is that macro defined below becomes part of
    export-libs subpackage. %end will terminate post/postun immediately
    without such side-effect.
    
    Signed-off-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>