Fix #33183: cycles bump mapping was not executed with only an AO node in a material.

intern/cycles/kernel/shaders/node_ambient_occlusion.osl

@@ -19,6 +19,7 @@
 #include "stdosl.h"
 
 shader node_ambient_occlusion(
+	normal NormalIn = N,
 	color Color = color(0.8, 0.8, 0.8),
 	output closure color AO = ambient_occlusion())
 {

intern/cycles/render/nodes.cpp

@@ -1578,6 +1578,8 @@ void HoldoutNode::compile(OSLCompiler& compiler)
 AmbientOcclusionNode::AmbientOcclusionNode()
 : ShaderNode("ambient_occlusion")
 {
+	add_input("NormalIn", SHADER_SOCKET_NORMAL, ShaderInput::NORMAL, true);
+
 	add_input("Color", SHADER_SOCKET_COLOR, make_float3(0.8f, 0.8f, 0.8f));
 	add_output("AO", SHADER_SOCKET_CLOSURE);
 }