JUnit is required if you build from source

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@931436 13f79535-47bb-0310-9956-ffa450edef68

docs/manual/install.html

@@ -620,6 +620,11 @@ still need to
 make the JARs available as described under
 <a href="#installing">Installing Ant</a>.</p>
 
+<p>As of version 1.7.0 Ant has a hard dependency on JUnit and you must
+  install it manually into <code>lib/optional</code> (download it from
+  <a href="http://junit.org/" target="_top">JUnit.org</a>) if you are
+  using a source distribution of Ant.</p>
+
 <p>Your are now ready to build Ant:</p>
 <blockquote>
   <p><code>build -Ddist.dir=&lt;<i>directory_to_contain_Ant_distribution</i>&gt; dist</code>&nbsp;&nbsp;&nbsp;&nbsp;(<i>Windows</i>)</p>