ant task to delete build result
One answer
As far as I know there is no such task. You would typically not run a build that is not necessary. If there are no changes, the built won't run. You can create your own ant tasks however. Look at http://ryehle.wordpress.com/2011/12/21/adding-a-custom-ant-task-to-your-build-toolkit/ for a description. That blog from Robin contains a lot more interesting content too. This might be also interesting if you decide to create a custom ant task. It shows some build API: https://jazz.net/library/article/807