nir: Bail on clip/cull distance lowering if GLSL IR already did it.
We have a GLSL IR pass to convert clip/cull distance float arrays into vec4 arrays. In ff281e62 , we attempted to skip this pass if the GLSL IR lowering had already run. But, that code was not quite right, as we forgot to strip away the per-vertex IO array layer for geometry and tessellation shader varyings. If the GLSL IR pass has run, the variables will not be marked as "compact". So we can simply check that and bail. Reviewed-by: Timothy Arceri <email@example.com>