I forgot to include the require:
------------snip---------------------
require 'find' # oops!
dirs = ["jruby-1.0.3"]
excludes = []
for dir in dirs
  folder = ''
  Find.find(dir) do |path|
    if FileTest.directory?(path)
      if excludes.include?(File.basename(path))
        Find.prune       # Don't look any further into this directory.
      else
        next
      end
    else
      if folder != File.dirname(path)
        folder = File.dirname(path)
        puts 'SetOutPath "' + folder + '"'
      end
      puts 'File       "' + path + '"'
    end
  end
end
-----------------------end snip-------------------