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.h

@@ -31,6 +31,7 @@ class GlfwAdapter : public PlatformUIAdapter {
   double GetDisplayPixelsPerInch() const override;
   std::pair<int, int> GetFramebufferSize() const override;
   std::pair<int, int> GetWindowSize() const override;
+  bool IsGPUAccelerated() const override;
   void PollEvents() override;
   void SetClipboardString(const char* text) override;
   void SetVSync(bool enabled) override;