fu_stream_blksize

# File lib/bundler/vendor/fileutils/lib/fileutils.rb, line 1078
    def fu_stream_blksize(*streams)
      streams.each do |s|
        next unless s.respond_to?(:stat)
        size = fu_blksize(s.stat)
        return size if size
      end
      fu_default_blksize()
    end