private String createTemporaryPreinstallFile() {
   try {
     File tempFile = File.createTempFile("preinstall", null);
     tempFile.deleteOnExit();
     InstallUtil.copyResourceToFile("/gnu/io/installer/resources/macosx/preinstall", tempFile);
     String absPath = tempFile.getAbsolutePath();
     Process p = Runtime.getRuntime().exec(new String[] {"chmod", "a+x", absPath});
     p.waitFor();
     return absPath;
   } catch (Throwable t) {
   }
   return null;
 }