Is there a recommended way to terminate an in-progress ant build from within the build itself?

The behavior I'm looking for is similar to the "buildNotNecessary" flag on CompleteBuildTask or the Jazz SCM "build only if changes were accepted", but executed by the ant build script itself. I'm currently emulating this function by calling:

getTeamBuildRequestClient().makeBuildIncomplete(getBuildResultHandle(), IBuildResult.PROPERTIES_REQUIRED, getProgressMonitor());

getTeamBuildClient().delete(getBuildResultHandle(), getProgressMonitor());

from a custom ant task and then invoking the ant <fail> task. The build is correctly terminated and the result deleted, but the build loop then catches and writes an exception after the ant build completes (because it attempts to call makeBuildComplete on a build result that has already been deleted).

Is there a graceful way to accomplish this via the Java API from within an in progress ant task? Is there something that would allow me to notify the build loop via ant properties that the build should be abandoned / removed? Or is this something I should be attempting via a pre-build participant (stop the build before it starts) or post-build participant (detect that an ant property has been set and delete the build result after completion)?