Use a target dependency rather than a file dependency when doing a core build of the ocaml examples.  This change sorted out a dependency issue I noticed for the test_ocaml_psc target.
Use a target dependency rather than a file dependency when doing a core
build of the ocaml examples.  This change sorted out a dependency
issue I noticed for the test_ocaml_psc target.

svn path=/trunk/; revision=10343

FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot