I'm using a build.xml file that has the following <path> in it:

<path id="compile.classpath">
  <pathelement location="${basedir}"/>

  <fileset dir="${basedir}/lib" >
   <include name="*.jar" />
  </fileset>

  <!-- Include all elements that Tomcat exposes to applications -->
  <pathelement location="${catalina.home}/common/classes"/>
  <fileset dir="${catalina.home}/common/endorsed">
   <include name="*.jar"/>
  </fileset>
  <fileset dir="${catalina.home}/common/lib">
   <include name="*.jar"/>
  </fileset>
  <pathelement location="${catalina.home}/shared/classes"/>
  <fileset dir="${catalina.home}/shared/lib">
   <include name="*.jar"/>
  </fileset>
</path>


This only works for tomcat 1.5 and below, I think, which have the "common"
and "shared" folders in the tomcat root directory (tomcat 1.6 and up have a
"lib" folder only under the tomcat root). This build.xml needs to be used
by people running old and new Tomcat versions, so I want to be able to check
for these directories, and only include them if they are present (otherwise
the ant script doesn't work), and otherwise run the equivalent of:

<path id="compile.classpath">
  <pathelement location="${basedir}"/>

  <fileset dir="${basedir}/lib" >
   <include name="*.jar" />
  </fileset>

  <fileset dir="${catalina.home}/lib">
   <include name="*.jar"/>
  </fileset>
</path>

But I'm having no luck accomplishing this. Is this possible? If so, how?
If this makes no sense to try and do, what am I missing and how should I
accomplish this?

Thanks.