First thing you should do is wash the truck. Next, clay the glass to ensure there are no impurities embedded in the glass. If the scratches are still there after wash and clay, I suggest polishing the glass.
A lot of people have had success hand polishing using Adam's Revive Polish. Depending on how severe the scratches are, you may have to use a Porter Cable with Adam's Swirl & Haze Remover. You need to be very careful using a machine on the glass as you can easily crack the glass with any amount of heat. Take your time with this one.
If machine polish does not remove the scratches, you may have to wet sand it.