Make 20-grub.install to generate debug BLS when MAKEDEBUG is set
    
    If MAKEDEBUG=yes in /etc/sysconfig/kernel, then a debug menu entry should
    be created. So for BLS, a debug configuration file has to be created that
    contains debug kernel command line parameters.
    
    Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>