使用复制任务中的存在条件。

Use the Exists condition on Copy task.

<CreateItem Include="*.xml">
  <Output ItemName="ItemsThatNeedToBeCopied" TaskParameter="Include"/>
</CreateItem>

<Copy SourceFiles="@(ItemsThatNeedToBeCopied)"
      DestinationFolder="$(OutputDir)"
      Condition="Exists('%(RootDir)%(Directory)%(Filename)%(Extension)')"/>