some ant tasks use the wrong build directory [LUCENE-3651]

I noticed locally i had a build/ under the root with an analyzers.jar in it... i wondered where this came from,
especially since it means we are recompiling this jar in some cases or not cleaning it correctly.

reproduce quickest by making a build/ in the root of your checkout, chmod it 000 and run 'ant javadocs':
BUILD FAILED
/home/rmuir/workspace/lucene-trunk/build.xml:32: The following error occurred while executing this line:
/home/rmuir/workspace/lucene-trunk/solr/common-build.xml:219: The following error occurred while executing this line:
/home/rmuir/workspace/lucene-trunk/lucene/build.xml:229: The following error occurred while executing this line:
/home/rmuir/workspace/lucene-trunk/lucene/common-build.xml:328: The following error occurred while executing this line:
/home/rmuir/workspace/lucene-trunk/lucene/common-build.xml:812: Directory /home/rmuir/workspace/lucene-trunk/build/common/classes/java creation was not successful for an unknown reason

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Migrated from [LUCENE-3651](https://issues.apache.org/jira/browse/LUCENE-3651) by Robert Muir (@rmuir)

Start with the build directory references in build.xml, solr/common-build.xml, lucene/build.xml, and lucene/common-build.xml. Reproduce the failure by creating a root build/ with mode 000 and running ant javadocs; done means the tasks use the intended build directory and no incorrect root build artifacts are created.

Written by the indexing model from the issue text.