Gem::Installer::FakePackage#extract_files

# File tmp/rubies/ruby-3.0.5/lib/rubygems/installer.rb, line 128
def extract_files(destination_dir, pattern = '*')
  FileUtils.mkdir_p destination_dir

  spec.files.each do |file|
    file = File.join destination_dir, file
    next if File.exist? file
    FileUtils.mkdir_p File.dirname(file)
    File.open file, 'w' do |fp|
      fp.puts "# #{file}"
    end
  end
end