To run an Ant buildfile in the Workbench:
The Ant buildfile will run on the selected targets. Unless you disabled the Capture output option on the Main tab, the console displays any applicable execution results as the buildfile runs.
These steps create a persisted launch configuration. The newly created configuration will appear in the launch history under Run > External Tools and will be available in the launch configuration dialog which is opened by clicking Run > External Tools > External Tools....
Running external tools
Modifying the Ant classpath
Using a different version of Ant
Adding new Ant tasks and types