Just pretend you are playing Pokemon Go!
It really depends on how extensive the photo requirements are.
If it's just the front of the building, I can usually do this in my car. I'll try to find a parking spot where I can face the front of the building and shoot the photo. Considering all the things people do in their cars, a photo is nothing unusual.
In truth, with cell phone use these days, taking photos of anything doesn't look out of place. Just act natural and you likely won't draw suspicion.