compiler: Mark clip/cull distance arrays as compact before lowering.

nir_lower_clip_cull_distance_arrays() marks the combined clip/cull
distance array as compact.  However, when translating in from GLSL
or SPIR-V, we were not marking the original float[] arrays as compact.

We should do so.  That way, we can detect these corner cases properly.

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
(cherry picked from commit ef99f4c8)
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>