Our coverage reports use clover as part of our cruisecontrol build. We have had some fun over time with X11 display issues when cruise calls the parts of the ant script which launches the clover graphing tool.
On a normal build you would just add -Djava.awt.headless=true on a jdk 1.4+ machine, but we struggled to get this passed to ant. Environmental variables like ANT_OPTS do not seem to be passed by cruise.
However salvation is now at hand, it is possible to pass these kinds of flags to the ant task as part of the control.xml file.
<ant buildfile="myproject/etc/build.xml" target="cruise-build" multiple="1" useLogger="false" >