title: rpmbuild spec file ignore file that does not exist
body: <p>Is it possible to tell an rpmbuild spec file to ignore a file in the files list if it doesn't exist?</p>
  
  <p>Something like:</p>
  
  <pre><code>%files
  %{existingfile}
  if [ -f %{dtdfile} ]; then
  %{dtdfile}
  fi
  </code></pre>