Fixed build error under Linux
Fixed build error under Linux

scamille/simbody,Gjacquenot/simbody,robojukie/simbody,Gjacquenot/simbody,scamille/simbody,robojukie/simbody,simbody/simbody,elkingtonmcb/simbody,chrisdembia/simbody,chrisdembia/simbody,simbody/simbody,elkingtonmcb/simbody,elen4/simbody,elkingtonmcb/simbody,scamille/simbody,elen4/simbody,chrisdembia/simbody,robojukie/simbody,Gjacquenot/simbody