Build with LTO
    
    LTO has been explicitely disabled because of build issue with the
    optimization. It seems however that these issues are fixed now and
    Fedora guidelines ask to use default build options unless absolutely
    necessary. Reenable LTO.
    
    Also clean the specfile a little: no need for all these commented out
    lines related to git sources.
    
    Resolves: RHEL-46715
    Signed-off-by: Jerome Marchand <jmarchan@redhat.com>