[patch] Fix live/boot/hybridcd extras location on disk

This patch makes the file put in the [bootcd|livecd|hybridcd]_extras folder actually do what the comment tells it will do:
follow the exact folder structure on the livecd.

Without the patch all files will end up below subfolders of extras,
with this patch it's possible to e.g. add files to the desktop and whatnot.