RivieraPro tip: how to display wall-clock sim time

will display wall-clock simulation run time upon simulation end; thanks Sunil at Aldec:

  set start_time [clock clicks -millisec]
  run $SIMTIME ; # pass sim time (you must set this previously)
  set run_time [expr ([clock clicks -millisec]-$start_time)/1000.]
  puts "Sim  Time: $run_time sec. \n"