fix: Fix testrender GPU regression with bad destruction order

src/testrender/optixraytracer.cpp

@@ -1253,7 +1253,7 @@ OptixRaytracer::finalize_pixel_buffer()
 void
 OptixRaytracer::clear()
 {
-    shaders().clear();
+    SimpleRaytracer::clear();
     OPTIX_CHECK(optixDeviceContextDestroy(m_optix_ctx));
     m_optix_ctx = 0;
 }

src/testrender/simpleraytracer.cpp

@@ -1101,4 +1101,10 @@ SimpleRaytracer::render(int xres, int yres)
 
 
 
+void
+SimpleRaytracer::clear()
+{
+    shaders().clear();
+}
+
 OSL_NAMESPACE_EXIT

src/testrender/simpleraytracer.h

@@ -82,7 +82,7 @@ class SimpleRaytracer : public RendererServices {
     virtual void prepare_render();
     virtual void warmup() {}
     virtual void render(int xres, int yres);
-    virtual void clear() {}
+    virtual void clear();
 
     // After render, get the pixels into pixelbuf, if they aren't already.
     virtual void finalize_pixel_buffer() {}

src/testrender/testrender.cpp

@@ -368,7 +368,7 @@ main(int argc, const char* argv[])
 
     // We're done with the shading system now, destroy it
     rend->clear();
-    delete rend;
     delete shadingsys;
+    delete rend;
     return EXIT_SUCCESS;
 }