<condition property="lib.dir" value="${lib.dir.gtk}" else="${lib.dir.win}">
    <or>
      <and>
        <isset property="${build.os}" />
        <equals arg1="${build.os}" arg2="gtk" />
      </and>
      <and>
        <not><isset property="${build.os}" /></not>
        <os name="Linux" />
      </and>
    </or>
  </condition>


<!--
  if ( ( isset($build.os) && $build.os == 'gtk' ) || ( !isset($build.os) && $os.name == 'Linux' ) )
  {
    $lib.dir = $lib.dir.gtk;
  }
  else
  {
    $lib.dir = $lib.dir.win;
  }
-->