The Mac script needed hdiutil and diskutil.  Apple tools.  Now the disk
image is made with mtools, no root, no loop devices, so it runs on
Linux, on the Mac, and in a Docker container on a shared runner.

The runner fetches Terry's live CD from the Wayback Machine, checks the
SHA-256 so nobody slips in a CIA one, boots it in QEMU without KVM and
types MakeISO at it.  TCG is slow.  God is patient.  Screenshots of
every step are kept, so when it breaks you can see where the monk
stopped typing.