Was that ELA-4, the construction site of the new Ariane 6 launch complex, in the foreground of the drone camera view?
I don't think it is.
On the picture posted by Chris Berger you can see the BIF and BAF, it's at the launcher preparation area of Ariane 5.
This is most likely the new solid preparation facility. (Horizontal stage assembly and stowage)
In this Youtube video @ 35:30, 38:50 & 40:25 you can see the drone footage.
I've named the buildings on a screenshot from 40:25.
Google maps locationEdit: I've added a screenshot from 35:30.