# File lib/mkmf.rb, line 83
def install_dirs(target_prefix = nil)
  if $extout
    dirs = [
      ['RUBYCOMMONDIR', '$(extout)/common'],
      ['RUBYLIBDIR',    '$(RUBYCOMMONDIR)$(target_prefix)'],
      ['RUBYARCHDIR',   '$(extout)/$(arch)$(target_prefix)'],
      ['extout',        "#$extout"],
      ['extout_prefix', "#$extout_prefix"],
    ]
  elsif $extmk
    dirs = [
      ['RUBYCOMMONDIR', '$(rubylibdir)'],
      ['RUBYLIBDIR',    '$(rubylibdir)$(target_prefix)'],
      ['RUBYARCHDIR',   '$(archdir)$(target_prefix)'],
    ]
  else
    dirs = [
      ['RUBYCOMMONDIR', '$(sitedir)$(target_prefix)'],
      ['RUBYLIBDIR',    '$(sitelibdir)$(target_prefix)'],
      ['RUBYARCHDIR',   '$(sitearchdir)$(target_prefix)'],
    ]
  end
  dirs << ['target_prefix', (target_prefix ? "/#{target_prefix}" : "")]
  dirs
end