错误日志为：
validateRenderPassDescriptor:757: failed assertion `Texture at colorAttachment[0] has usage (0x01) which doesn't specify MTLTextureUsageRenderTarget (0x04)'
引起崩溃的Unity 位置：
UnityAppController -> startUnity -> [self showGameUI] -> UnityRepaint() -> UnityPlayerLoop()
简单屏蔽导致现象：unity场景无法加载成功
解决方式为：
Xcode->Product->Scheme->Edit Scheme, disable Metal API
