Fixed compilation on FreeBSD.

git-svn-id: http://svn.boost.org/svn/boost/trunk@86560 b8fc166d-592f-0410-95f2-cb63ce0dd405
Make the handling of actions that produce multiple targets more correct.

git-svn-id: http://svn.boost.org/svn/boost/trunk@86561 b8fc166d-592f-0410-95f2-cb63ce0dd405