Fix build against musl

[attilaolah]

What does this PR do?

Makes codebase-memory-mcp build against musl libc.

• Allow the toolchain to pass the linker via the usual $LD env var, instead of hard-coding ld.
• Provide fallback values for phase and log when null, since passing those to %s with musl-gcc is UB.

Checklist

• Every commit is signed off (git commit -s) — required, CI rejects
  unsigned commits (DCO, see CONTRIBUTING.md)
• Tests pass locally (make -f Makefile.cbm test -j$(nproc))
• Lint passes (make -f Makefile.cbm lint-ci)
• New behavior is covered by a test (reproduce-first for bug fixes)

[github-actions]

Thanks for opening this — it has been seen, and it is queued.

This note is automated, but it is not a brush-off: it exists so you know where your PR stands instead of having to guess from silence.

Current review status: working through a backlog. 0.9.1-rc.1 is out, so the release freeze that held reviews is over — but it left a large queue of open pull requests behind it, and we are reading through them oldest-first. The background is in discussion #1144.

What that means for this PR, concretely:

• It will not be closed for inactivity. No stale bot touches pull requests here.
• It may still sit a while before a human reads it. That is on us, not on you.
• Older PRs are read first, so a recent one is not being skipped — it is behind a queue.

Things that will genuinely speed it up whenever review does happen:

• Keep it rebased on main — the tree is moving quickly right now, and a conflicting branch cannot be reviewed as the diff you intended.
• Get CI green, or say which failures you believe are pre-existing.
• Keep the change to one claim. Bundled features and refactors get split before they get merged, which costs you a round trip.
• Every commit needs a sign-off (git commit -s) — CI enforces DCO.

If this fixes a bug, a reproduction we can run is worth more than a description of the symptom.

Thanks for contributing, and sorry in advance for the wait.

[attilaolah]

There seem to be multiple pre-existing linter warnings, none of them seem to be related to this change.

[attilaolah]

Many of the grammar tests are also failing, not sure yet whether they are caused by my change.

FAIL tests/test_grammar_probe_e.c:830: ASSERT(m.ok)

Final results:

────────────────────────────────────────────
  8761 passed, 953 failed, 10 skipped
────────────────────────────────────────────

Plus many leaks detected by the sanitizer.