radv: skip radv_remove_varyings for mesh shaders

Fixes compilation of a Talos Principle 2 shader.

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Fixes: 9fa9782c17 ("radv: stop compiling a noop FS when the application doesn't provide a FS")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25659>

src/amd/vulkan/radv_pipeline_graphics.c

@@ -1627,6 +1627,12 @@ radv_pipeline_needs_noop_fs(struct radv_graphics_pipeline *pipeline, const struc
 static void
 radv_remove_varyings(nir_shader *nir)
 {
+   /* We can't demote mesh outputs to nir_var_shader_temp yet, because
+    * they don't support array derefs of vectors.
+    */
+   if (nir->info.stage == MESA_SHADER_MESH)
+      return;
+
    bool fixup_derefs = false;
 
    nir_foreach_shader_out_variable (var, nir) {