Avoid returning duplicate libs when looking for g77 runtime on windows: just return the first one (first being defined by the order of the list of libpath to look in).
Avoid returning duplicate libs when looking for g77 runtime
on windows: just return the first one (first being defined by
the order of the list of libpath to look in).

cournape/numscons,cournape/numscons,cournape/numscons