null implementation of the render graph builder

src/renderer/null/null.c

@@ -142,4 +142,15 @@ void RT_RENDERER_API_FN(CmdFlushRenderTargetWrite)(rt_command_buffer_handle cmdb
                                                    rt_render_target_handle render_target) {
     RT_UNUSED(cmdbuf_handle);
     RT_UNUSED(render_target);
+}
+
+rt_render_graph_builder RT_RENDERER_API_FN(CreateRenderGraphBuilder)(void) {
+    rt_render_graph_builder b = {
+        .obj = NULL,
+    };
+    return b;
+}
+
+void RT_RENDERER_API_FN(DestroyRenderGraphBuilder)(rt_render_graph_builder *builder) {
+    RT_UNUSED(builder);
 }