feat: bump instrument-hooks to not use stubs on macos

[GuillaumeLagrange]

This adds support for macos to exec-harness

[greptile-apps]

Greptile Summary

This PR bumps the instrument-hooks submodule from ecdf31a to b9ddb5b to ship a macOS-compatible build of the native C library, replacing the previous noop/stub path on that platform. The build.rs already handles this gracefully — it compiles dist/core.c, sets cfg(use_instrument_hooks) on success, and falls back to a noop implementation on failure.

• Submodule bump (crates/instrument-hooks-bindings/instrument-hooks): new commit adds proper macOS support in the distributed C source, so the real instrument-hooks implementation will now compile and be active on macOS instead of the noop stub.
• No Rust code changes: build.rs and lib.rs are unchanged; the non-Linux timestamp path (ffi::instrument_hooks_current_timestamp()) was already wired up and will now be reached on macOS.

Confidence Score: 4/5

Safe to merge — the only change is a submodule bump and the build system already falls back gracefully to a noop if the C library fails to compile.

The change is a single submodule pointer update. The build fallback means a bad compile would leave macOS in the same stub state as before, so there is no regression risk. The one gap is that exec-harness unit tests do not run on macOS in CI, so any test assertions that exercise the instrument-hooks path are untested on the newly enabled platform.

The CI workflow (.github/workflows/ci.yml) could benefit from running exec-harness tests on macOS now that the real implementation is active there.

Important Files Changed

Filename	Overview
crates/instrument-hooks-bindings/instrument-hooks	Submodule bumped from ecdf31a to b9ddb5b to include macOS support in dist/core.c; build.rs will now set cfg(use_instrument_hooks) on macOS enabling the real implementation instead of the noop stub.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[build.rs compiles dist/core.c] -->|Success| B[use_instrument_hooks cfg set]
    A -->|Failure| C[Noop fallback other_impl]
    B --> D{Target OS}
    D -->|Linux| E[current_timestamp via nix clock_gettime]
    D -->|macOS now enabled| F[current_timestamp via FFI]
    D -->|Other| F
    E --> G[linux_impl InstrumentHooks]
    F --> G
    C --> H[other_impl InstrumentHooks noop]

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[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 7 untouched benchmarks

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_{Comparing cod-2709-bump-instrument-hooks-for-exec-harness (d7e7745) with main (0496dcd)}