update AssetBundleBuilder

unity2021开始不再支持内置构建管线。

Assets/YooAsset/Editor/AssetBundleBuilder/BuildTasks/TaskPrepare.cs

@@ -16,6 +16,11 @@ namespace YooAsset.Editor
 
 			var buildParameters = buildParametersContext.Parameters;
 
+#if !UNITY_2021_1_OR_NEWER
+			if (buildParameters.BuildPipeline == EBuildPipeline.BuiltinBuildPipeline)
+				throw new Exception($"Unity2021 or newer not support {nameof(EBuildPipeline.BuiltinBuildPipeline)}, Please use {nameof(EBuildPipeline.ScriptableBuildPipeline)}");
+#endif
+
 			// 检测构建参数合法性
 			if (buildParameters.BuildTarget == BuildTarget.NoTarget)
 				throw new Exception("请选择目标平台");