Properly detect Ruby 1.9 on Windows.

* build/generator/gen_win.py:
  (WinGeneratorBase._find_ruby): Pass the -W0 option to ruby.exe to stifle
   the warning about Config being deprecated and that RbConfig should be
   used.  Ruby just uses RbConfig anyway.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1480344 13f79535-47bb-0310-9956-ffa450edef68