title: Ant conditional failure upon executable failure
body: <p>I have the following ant target: </p>
  
  <pre><code>&lt;target name="refactor-ids"&gt;
      &lt;echo&gt;Refactor IDs&lt;/echo&gt;
      &lt;exec executable="perl" dir="${basedir}"&gt;
          &lt;arg value="script.pl" /&gt;
          &lt;arg value="input.xml" /&gt;
  
      &lt;/exec&gt; 
  &lt;/target&gt;
  </code></pre>
  
  <p>If the executable fails for any reason (script.pl doesnt exist, etc) the build will resolve as successful.  How do I establish conditional build success upon the success of this executable? </p>