Fix T88096: Baking with OptiX and displacement fails

Using displacement runs the shader eval kernel, but since OptiX modules are not loaded when
baking is active, those were not available and therefore failed to launch. This fixes that by falling
back to the CUDA kernels.

intern/cycles/device/device_optix.cpp

@@ -726,7 +726,11 @@ class OptiXDevice : public CUDADevice {
       }
     }
     else if (task.type == DeviceTask::SHADER) {
-      launch_shader_eval(task, thread_index);
+      // CUDA kernels are used when doing baking
+      if (optix_module == NULL)
+        CUDADevice::shader(task);
+      else
+        launch_shader_eval(task, thread_index);
     }
     else if (task.type == DeviceTask::DENOISE_BUFFER) {
       // Set up a single tile that covers the whole task and denoise it