* test/win32ole/test_err_in_callback.rb (TestErrInCallBack#setup):
  allow using different drive for source and build directories.
  this may fixes a minor problem of r39834.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39837 b2dd03c8-39d4-4d8f-98ff-823fe69b080e