You can put farms in the desert. Some of the most productive farmland is in deserts. Arizona and California are both noted for producing large quantities of high-quality cotton.
It comes with its own set of problems, but deserts are not dealbreakers for agriculture as the GP suggests.
Which also brings up a question if indoor farms recycle their water? At the very least, I might expect the transpiration rate to be lower, lowering water use.
Incredible amount of lettuce is grown in Arizona as well!