Have you tried making a backup of the directory giving the error and copying the libs that work to the location? If that works, it should be something simple like download corruption. If it does not work, it means there is a problem with the way you are running the tests.
On my Mac, I run with run.sh:
LIBS="$XITH_EXTERNAL/gluegen/macosx-universal $XITH_EXTERNAL/jogl/macosx-universal $XITH_EXTERNAL/lwjgl/natives $XITH_EXTERNAL/joal/natives"
java -ea -Djava.library.path=$LIBS -classpath $CLASSPATH -Xms128m -Xmx128m -XX:+AggressiveOpts $ARGS