Automates the build of Linux From Scratch 6.7.

This adds/replaces files in the existing filesystem.  At the end of the build
BusyBox is still there but most of the symlinks to it have been replaced with
the corresponding gnu tools.

This does not attempt to replace the existing toolchain or C library, although
there's no reason you can't run a separate script to do that before running
this build.

We're not building grub because bootloaders are both extremely target-specific
(which CPU, which board, which boot media...  Booting an ARM from the network
or booting MIPS from flash isn't really grub's thing).  You'll have to set up
your own bootloader as appropriate for your hardware.  (QEMU has a built-in
bootloader in the -kernel option.)

Note that we skip the various "move stuff from /usr/bin to /bin" steps
because /lib, /bin, and /sbin are all symlinks to the appropriate directory
under /usr so we've already combined all that stuff already.  (That split
happened when Ken and Dennis filled up their original root filesystem's RK05
disk pack on the PDP-11 they developed Unix on in 1971, so they let their
operating system files leak into the second disk, where all the user
directories lived.  They eventually added a third disk on /home and moved the
user directories to there, but kept the OS straddling two disks.  These days
between initramfs and cheap multi-terrabyte drives that split is a useless
historical artifact kept alive by people blindly following procedures they
no longer understand.  Don't get me started on /opt.)