Turn off reflection and shadow in simulate when a GPU is not present.

Note that The GLFW adapter currently assumes that a GPU is always present, so this new code path is never reached at the moment.

PiperOrigin-RevId: 504617048
Change-Id: I04a323c33d9cff73686d39e4a6676ca6a4484c98

simulate/glfw_adapter.cc

@@ -129,6 +129,10 @@ std::pair<int, int> GlfwAdapter::GetWindowSize() const {
   return {width, height};
 }
 
+bool GlfwAdapter::IsGPUAccelerated() const {
+  return true;
+}
+
 void GlfwAdapter::PollEvents() {
   Glfw().glfwPollEvents();
 }