Ticket 49347 - reproducable build numbers
    
    Bug Description:  in order to make builds reproducible.
    See https://reproducible-builds.org/ for why this is good
    and https://reproducible-builds.org/specs/source-date-epoch/
    for the definition of this variable.
    
    Fix Description:  Add the environment valiable as requested for
    reproducable builds.
    
    https://pagure.io/389-ds-base/issue/49347
    
    Author: Bernhard M. Wiedemann
    
    Review by: wibrown