This function manages mounting the mountpoints for the chroot(s) in preparation for the images of the live media. It also runs <<changing_the_build_process,the inner chroot preparation script>>. Returns `chrootdir` (same as the paramater provided).
===== chrootdir
The directory where the filesystem tree for the chroot lies. Absolute path only.
===== chroot_hostname
The hostname to use for the guest.
NOTE: This paramater may be removed in future versions.
===== cmd
The command to run inside the chroot once all the mountpoints are set up.
==== chrootUnmount(_chrootdir_)
Unmount the mounts set up in <<chroot_em_chrootdir_em_em_chroot_hostname_em_em_cmd_em_root_pre_build_sh,chroot()>>.
===== chrootdir
See <<chrootdir>>.
==== chrootTrim(_build_)
This function performs some cleanup and optimizations to the chroot(s).