Fix Ant's bundled jar generation

The package-for-store task fails because it refers to the dist/lib directory now missing on master:

$ git clone --depth 1 --branch master git@git.wur.nl:bioinformatics/pantools.git
...
$ cd pantools
$ ant package-for-store
...
-post-deploy:

deploy:

jar:

package-for-store:
     [echo] Packaging pantools into a single JAR at store/pantools.jar
    [mkdir] Created dir: /private/tmp/pantools/store

BUILD FAILED
/private/tmp/pantools/build.xml:80: /private/tmp/pantools/dist/lib does not exist.

Total time: 8 seconds