radv: remove NIR_PASS in radv_nir_lower_rt_abi

When NIR_DEBUG=serialize or NIR_DEBUG=clone is used, NIR_PASS recreates
nir_function_impl and nir_variable objects, causing use-after-free since
radv_nir_lower_rt_abi() keeps pointers to those in local variables.

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Marek Olšák <maraeo@gmail.com>
Reviewed-by: Georg Lehmann <dadschoorse@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37573>

src/amd/vulkan/nir/radv_nir_rt_shader.c

@@ -1992,7 +1992,8 @@ radv_nir_lower_rt_abi(nir_shader *shader, const VkRayTracingPipelineCreateInfoKH
    }
    shader->scratch_size = 0;
 
-   NIR_PASS(_, shader, nir_lower_returns);
+   /* This can't use NIR_PASS because NIR_DEBUG=serialize,clone invalidates pointers. */
+   nir_lower_returns(shader);
 
    nir_cf_list list;
    nir_cf_extract(&list, nir_before_impl(impl), nir_after_impl(impl));