The build.properties seems to be setup correctly according to the FRC tutorial on adding 3rd party libraries:
Code:
# Project specific information
package=org.usfirst.frc.team2972.robot
robot.class=${package}.Robot
simulation.world.file=/usr/share/frcsim/worlds/GearsBotDemo.world
userLibs=${user.home}/navx-mxp/java/lib/navx_frc.jar
Is there another issue that could potentially be affecting the classpath?