Spinel is Matz's ahead-of-time Ruby compiler. Start from a working CARLOS
app built with it: `gh repo clone paulca/lpay`, directory `spinel/`.
Read its `README.md` and `BUILD-arm64.md`. It uses tep (a Sinatra-style
layer that drives Spinel) and `patches/tep-carlos.patch`, which teaches
tep the platform's socket contract and fixes `Content-Length` for
multi-byte UTF-8. Spinel, tep and spinelkit are checked out at tep's pin
in `~/.local/share/bakeoff-toolchains/spinel-src/`, and an arm64 Spinel
built inside the arm64 root is at
`~/.local/share/bakeoff-toolchains/spinel-arm64/` (see
`docs/toolchains.md`). Copy what you need into `apps/spinel/` rather than
editing those checkouts.