Update tcl epa_build configuration so that it works on MinGW/MSYS.
Update tcl epa_build configuration so that it works on MinGW/MSYS.

svn path=/trunk/; revision=12918

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