anv: call nir_shader_gather_info early

Shader info is needed for mesh in linking (in nir_lower_io_to_scalar_early, see commit 5e144454) and will be needed once MR !17622 (merged) (anv: work around for per-prim attributes corruption) lands.

This fixes func.mesh.ext.outputs.per_primitive.unused crucible test on DG2. (I didn't know this test wasn't fixed by 5e144454, because I was testing with !17622 (merged) merged-in, which added its own nir_shader_gather_info before nir_lower_io_to_scalar_early).