I've released a new extension for bld to easily execute JBang commands and scripts:

@BuildCommand(summary = "Runs JBang script")
public void jbang() throws Exception {
    new JBangOperation()
            .fromProject(this)
            .jBangArgs("--quiet")
            .script("path/to/script.java")
            .args("foo", "bar")
            .execute();
}

Full access to the entire JBang ecosystem with a single extension!