We are using a shell script that prepares some environment (variables and paths) and then starts ant with additional parameters. In current state this workflow is not supported by the ivy job type as it insists on using plain ant as the builder.
The builder should be irrelevant for the ivy job as it is irrelevant for the simple job. It can require ant installation to perform its own steps, but should not limit the builder to be ant only. It can be that it requires to know if the builder is ant-based or not to allow for ant targets output in console view etc.
The current work around for that:
Create an arbitrary ant folder and change the content of "ant" script to actually run our script