nir: allow nir_lower_clip_halfz to run in geometry shaders

the final output of gl_Position needs this transform, and geometry shaders
must write this value for stream 0 if rasterization is enabled

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5851>

src/compiler/nir/nir_lower_clip_halfz.c

@@ -56,7 +56,8 @@ lower_pos_write(nir_builder *b, struct nir_instr *instr)
 void
 nir_lower_clip_halfz(nir_shader *shader)
 {
-   if (shader->info.stage != MESA_SHADER_VERTEX)
+   if (shader->info.stage != MESA_SHADER_VERTEX &&
+       shader->info.stage != MESA_SHADER_GEOMETRY)
       return;
 
    nir_foreach_function(function, shader) {