File _service of Package clang

<services>
  <service name="download_url">
    <param name="url">https://github.com/llvm/llvm-project/releases/download/llvmorg-21.1.7/llvm-project-21.1.7.src.tar.xz</param>
    <param name="filename">llvm-project-21.1.7.src.tar.xz</param>
  </service>
</services>