How to use RTP’s parallax shaders in Unity VR

Unity’s new native VR support is a big improvement in regards to cost of rendering and thus performance. Unfortunately, things were “oversimplified” a little, and shaders do not get information about which eye is rendered for any given call.
Until there is an official solution to this problem, I am showing an easy hack to work around this issue, using Tomasz Stobierski’s Relief Terrain Shaders as an example.