ISPN-4413 PAX URL temporary files fill /tmp and cause issues on CI

https://issues.jboss.org/browse/ISPN-4413
The advantage of doing this in Ant is that it gurantees the directory will be created before any File.createTempFile() calls are made as the surefire JVM instance is started after the generate-sources step.

The other thing is that the temporary file location is initialized statically so changing the system property and creating the directory inside the test code won't work if a temporary file was created outside the tests previously.