fix case when not linking against libpthread
fix case when not linking against libpthread

This commit was SVN r655.

ggouaillardet/hwloc,ggouaillardet/hwloc,ggouaillardet/hwloc,shekkbuilder/hwloc,shekkbuilder/hwloc,shekkbuilder/hwloc,ggouaillardet/hwloc,shekkbuilder/hwloc