Burrito keys its on-host install directory on `{release}_erts-{ertsver}_{appver}`
and skips extraction when `_metadata.json` is already present for that version.
With a static `@version "0.1.0"` in mix.exs, every new build landed in the same
cached dir on the target host — silently running stale code.
Now @version resolves to `0.1.0+<BUILD_ID>` where BUILD_ID is the git short SHA
(or `dev-<timestamp>` fallback). scripts/build-linux.sh computes it on the host
and passes it through Dockerfile.build's ARG/ENV, so every commit produces a
distinct Burrito install dir and fresh extraction is guaranteed.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
