How to import constraints?

How do you export a rig with constraints (not baked) and import into UE4?

I imported this FBX rig with animation (from marketplace) into Maya, it has constraints with no keys on the ik foot.

I importing the same FBX file into UE4 and the constraints have been applied.

Please note I have not exported this FBX file, I imported it directly into both Maya and UE4.