fix(EXT-7): bundle musl NIF for Linux Burrito releases and container

[bougyman]

Summary

• Pre-compile mdex_native with TARGET_ABI=musl before mix release on Linux targets so the musl precompiled NIF is bundled instead of the glibc one detected from Ubuntu runners
• Same pre-compile step added to the container job (which also builds on Ubuntu but runs on Alpine)
• Add an Alpine/musl container smoke test (podman run ... lc version) after building the image to verify the musl NIF loads before publishing

Background

rustler_precompiled resolves which precompiled NIF to bundle at compile time from :erlang.system_info(:system_architecture). Ubuntu runners report a glibc triplet, so the glibc mdex_native NIF was being baked into Linux Burrito releases and the container image. The container runs Alpine 3.22 (musl), so the glibc NIF fails to load at runtime.

mdex_native v0.2.7 ships both x86_64-unknown-linux-gnu and x86_64-unknown-linux-musl (and aarch64 equivalents). Setting TARGET_ABI=musl before compiling mdex_native selects the musl variant. mix release then sees mdex_native already compiled in _build/prod/ and skips recompilation, bundling the musl .so.

TARGET_ABI is scoped to the mix deps.compile mdex_native step rather than set globally on mix release because cc_precompiler (used by exqlite) also reads that env var and produces a malformed triplet (--musl) when TARGET_ARCH/TARGET_OS are absent.

CRY-40 (v1.5.1) fixed the cross-OS NIF mismatch (Linux NIF going into macOS/Windows releases). This PR fixes the musl/glibc mismatch within Linux.

Test plan

• YAML validates syntactically (python3 yaml.safe_load)
• mix format --check-formatted clean
• mix credo --strict clean
• Tests: same 7 pre-existing GitTest failures (require a specific git remote state), 300/307 pass — unchanged from main
• CI: burrito-build Linux legs pre-compile mdex_native with musl NIF then build
• CI: container smoke test runs podman run ... lc version on Alpine and exits 0

Closes EXT-7

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[bougyman]

Rework: fixed two bugs in the original commit

What changed: Two correctness issues identified during self-review and fixed in the follow-up commit (4e9bdfa):

1. Pre-compile dep order (mix deps.compile mdex_native → mix deps.compile rustler_precompiled mdex_native): mix deps.compile with explicit dep names only compiles the named deps, not their transitive deps. mdex_native/native.ex uses use RustlerPrecompiled at compile time, so rustler_precompiled must be available in the Erlang code path before mdex_native is compiled. On a fresh CI runner (_build/ is empty), the original single-name command would fail with a CompileError: module RustlerPrecompiled is not loaded. Applied to both the burrito-build and container pre-compile steps.

2. Smoke test daemon mode (added -e LINEAR_CLI_DAEMON=false): The container image bakes in ENV LINEAR_CLI_DAEMON=true (intentional — that's what the daemon CMD needs). Without overriding it, podman run ... lc version starts the app in daemon mode, which ignores the version arg and stays alive indefinitely. The timeout-minutes: 1 guard would then kill it as a failure on every run. LINEAR_CLI_DAEMON=false routes through start_interactive() → CLI.main(["version"]) → prints version, exits 0.

Trade-offs: None. Both are straight correctness fixes.