fix bug in boost lib detection
fix bug in boost lib detection

if the boost libraries had a suffix, and BOOST_LIBRARIES_SUFFIX was unset,
some versions of bash would object to the resulting **. This makes sure
that can't happen

AveRapina/visionworkbench,fengzhyuan/visionworkbench,fengzhyuan/visionworkbench,AveRapina/visionworkbench,AveRapina/visionworkbench,AveRapina/visionworkbench,AveRapina/visionworkbench,fengzhyuan/visionworkbench,fengzhyuan/visionworkbench,DougFirErickson/visionworkbench,fengzhyuan/visionworkbench,DougFirErickson/visionworkbench,AveRapina/visionworkbench,DougFirErickson/visionworkbench,DougFirErickson/visionworkbench,fengzhyuan/visionworkbench,fengzhyuan/visionworkbench,DougFirErickson/visionworkbench,DougFirErickson/visionworkbench