Suffice it to say this is a bit specific for google. Erosion likely still builds up huge sandfields but I wonder if, given the force of the wind, they'd be moved from being spread out as an actual erg or if they would build up in a corner, such as into a valley (as an unrelated example).
Yes, and it would be the one place where the wind is calm.
Even from a theoretical standpoint, it’s impossible to have wind blowing on every point on a spherical surface. This comes from the impossibility of mapping differentiable tangent vector spaces to the sphere, but that’s an issue for math.se. Point is, there is always (always always, not just sometimes always) a point on a planet’s surface where the wind is calm. That point can move, change, disappear and reappear, or be multiple places simultaneously, but there must always be a point where the wind is still.
So, there’s always one spot where the wind is calm. That’s the spot where sand drops from the wind and doesn’t move again, and logically where your ergs will eventually be piled up. That one spot will be your “corner”.
Of course, as the spot where wind is calm changes, the ergs will move with it. Sand might circulate all over the planet before it eventually ends up back at the corner, but it will end up there eventually.