http://ant.apache.org/manual/Tasks/copydir.html

  <copydir src="${base.path}/lib/"
           dest="${build.path}/lib"
  />

  <copydir src="${base.path}/images/"
           dest="${build.path}/images"
  />

  <copydir src="${base.path}/src/com/"
           dest="${build.path}/com"
  />
  <copydir src="${base.path}/META-INF/"
           dest="${build.path}/META-INF"
  />

http://ant.apache.org/manual/Tasks/jar.html

<jar destfile="project.jar"
     basedir="${build.path}"
     includes="**/*.*"
     />