The movie sets that were used in “Patriots Day’’ are still standing on the South Shore, and apparently they won’t be going anywhere for a while. Both sets — one used to re-create the Boston Marathon finishing line on Boylston Street and the other a replica of a residential street in Watertown — are located at Union Point, a new mixed-use development at the old South Weymouth air base, and the company in charge of developing the property hopes they can be used again by filmmakers in the near future. “We purchased the sets from the ‘Patriots Day’ production company after they wrapped their shooting on the property,’’ said LStar managing partner Kyle Corkum. “Our intent was to retain the Boylston Street and Watertown sets so they could be re-used as back lots when people are filming at Union Point.’’ Corkum said the sets will remain in place and be available to people making movies and TV programs “until the day comes that they cannot be used any longer.’’