FileUtils::StreamUtils_#fu_stream_blksize

# File tmp/rubies/ruby-3.3.0/lib/fileutils.rb, line 2045
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