Using FileUtils

Let’s use FileUtils (instead of rd /s /q, etc.) as Tor erik Linnerud
pointed out.
http://rubyforge.org/pipermail/ironruby-core/2008-March/001317.html

http://sparcs.kaist.ac.kr/~tinuviel/download/IronRuby/patch-use-fileutils

Looks good - will apply for next update.

Thanks,
-John