anv: Insert holes for non-existant XFB varyings
Thanks to optimizations, it's possible for varyings to get deleted but still leave the variable there for nir_gather_xfb_info to find. If we get into this case, insert a hole.
Thanks to optimizations, it's possible for varyings to get deleted but still leave the variable there for nir_gather_xfb_info to find. If we get into this case, insert a hole.