We just tried that, with BREAD-Robot-Core.jar in C:\Users\David Boles\wpilib\java\current\lib, it crashes. If we add:
<fileset file="C:\Users\David Boles\wpilib\java\current\lib\BREAD-Robot-Core.jar"/>
<path id="classpath.path">
<fileset dir="${userLibs.dir}" includes="*.jar"/>
<fileset file="${wpilib.jar}"/>
<fileset file="${networktables.jar}"/>
<fileset file="${opencv.jar}"/>
<fileset file="${cscore.jar}"/>
here
<fileset dir="${userLibs}" erroronmissingdir="false"/>
</path>
in WPILib's build.xml it seems to work fine. Are we doing something wrong or is this an issue with WPILib's 3rd party library building process?