Add Vulkan backend placeholder with dynamic fallback

tests/gtest/dynamic_render_backend_test.cpp

@@ -12,3 +12,14 @@ TEST(DynamicRenderBackend, LoadsExperimentalOpenGLBackend)
 	EXPECT_EQ(renderer.OpenGLContext(), nullptr);
 #endif
 }
+
+TEST(DynamicRenderBackend, FallsBackWhenExperimentalVulkanUnavailable)
+{
+#ifndef OAK_ENABLE_DYNAMIC_RENDER_BACKEND
+	GTEST_SKIP() << "Dynamic render backend is not enabled in this build";
+#else
+	olive::DynamicRenderer renderer(QStringLiteral("vulkan"));
+	ASSERT_TRUE(renderer.Load());
+	EXPECT_EQ(renderer.OpenGLContext(), nullptr);
+#endif
+}