An automatic sprinkler system helped quell a late night fire in an industrial building in Brown Deer Saturday.   According to the North Shore Fire Department, crews were called to an industrial building at N 55^th Street and W Brown Deer Road around 9:50 PM.   Firefighters encountered heavy smoke as they entered the building.   Fire officials said the automatic sprinkler system was able to extinguish the fire as firefighters arrived.   Crews remained on scene for about 90 minutes.  The cause of the fire has yet to be determined.   Officials report extensive water and smoke  damage to the building but yet to determine a dollar amount of the damage.   No firefighters were injured and no one was in the building at the time of the fire.