vulkan: use push constants for builtin uniforms

when available

src/modules/graphics/vulkan/Shader.h

@@ -88,6 +88,7 @@ private:
 
 	VkPipeline computePipeline;
 
+	bool useBuiltinUniformPushConstant = false;
 	VkDescriptorSetLayout descriptorSetLayout;
 	VkPipelineLayout pipelineLayout;
 	std::vector<VkDescriptorPoolSize> descriptorPoolSizes;