intel/rt: Add a helper to create a trivial return shader

These are required for ray-tracing.  There are many cases where the
ray-tracing hardware may decide to execute some but not all of our
shaders.  In these cases, it needs a shader to execute at the end which
will pop the stack back to the shader which called traceRay().

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7356>

src/intel/compiler/brw_nir_rt.h

@@ -59,6 +59,10 @@ bool brw_nir_lower_shader_calls(nir_shader *shader,
 void brw_nir_lower_rt_intrinsics(nir_shader *shader,
                                  const struct gen_device_info *devinfo);
 
+nir_shader *
+brw_nir_create_trivial_return_shader(const struct brw_compiler *compiler,
+                                     void *mem_ctx);
+
 #ifdef __cplusplus
 }
 #endif