This shrinks the CFS size to 21k from nearly 64K. This will allow me to
kick the can down the road a bit with regards to supporting storage
seek/tell greater than 64K.
I'll get to it, but first, I want to assemble zasm with zasm!
On build, pack `parts/z80` into a CFS and embed it into the emulated
zasm executable as an fsdev. This will allow for the upcoming include
directive to have something to go to.
For now, this is useless except for inflating the emulated zasm's size.
With the help of the newly-introduced cfspack tool, we can mount a
filesystem in our emulated shell and play around. Read-only for now.
Unpacking incoming.