this patch fixes a problem with my prev patch (forgot a '\', and was
comparing x$platform with win32). And it fixes a problem where if
/usr/lib/python exists it's impossible to build win32 (without gcc) with
python. And it fixes a problem on windows, where //lib gets interpreted
as a windows share on computer LIB - it takes a while for cygwin to
figure out that there is no such computer.


git-svn-id: http://root.cern.ch/svn/root/trunk@13645 27541ba8-7e3a-0410-8455-c3a389f83636