feat: Build improvements

[jake-arkinstall]

Addresses two recent feedback items:

• zig pollutes the user's .cache/zig directory, which may grow large
• Selene manifests take too long to write

The first item is managed by providing zig with a cache dir, which subsequently sets ZIG_LOCAL_CACHE_DIR in the subprocess environment.

The second is managed by providing a complete_manifest bool flag to build(). When True, the manifest aims to be a complete picture of the build stages, for use with sharing and diagnosis. When False (default), less information is written to the manifest. At current this reduced information is in the form of stripping input artifact or intermediate artifacts in the manifest, keeping only the final binary.

[Copilot]

Pull request overview

Improves the Selene build pipeline by (1) scoping Zig’s cache to a configurable directory to avoid polluting users’ global Zig cache, and (2) reducing the size/time cost of writing Selene build manifests by optionally emitting a “complete” manifest.

Changes:

• Add complete_manifest to selene_sim.build.build() to optionally omit intermediate artifacts from the written manifest.
• Extend invoke_zig() to accept a cache_dir and propagate it via ZIG_LOCAL_CACHE_DIR; wire this through Helios/Selene builtin build steps.
• Adjust wheel build CI configuration (cibuildwheel rust setup steps; GitHub Actions cache restore keys).

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
selene-sim/python/selene_sim/build.py	Adds complete_manifest and conditionally trims manifest artifact entries.
selene-core/python/selene_core/build_utils/utils.py	Adds cache_dir support to Zig invocation via environment.
selene-core/python/selene_core/build_utils/builtins/selene.py	Passes Zig cache dir during final link step.
selene-core/python/selene_core/build_utils/builtins/helios.py	Passes Zig cache dir during compile/link steps across platforms.
pyproject.toml	Updates cibuildwheel rust setup steps (currently with an invalid rustup toolchain install invocation).
.github/workflows/build_wheels.yml	Enables cache fallback via restore-keys for build environment caching.

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[Copilot]

invoke_zig now captures stdout/stderr via Popen(..., stdout=PIPE, stderr=PIPE) but does not stream output to the console even when verbose=True, and all stdout is silently swallowed by callers (nobody uses the returned string). Consider keeping the previous behavior (inherit stdout; capture stderr for errors) or adding an explicit capture_output/stream_output option so builds don’t become opaque and long-running commands still show progress when desired.

[jake-arkinstall]

@copilot apply changes based on this feedback

[jake-arkinstall]

@copilot ...

[Copilot]

Fixed in commit f6edf63. invoke_zig now inherits stdout (streams to the console) when verbose=True, and suppresses it via DEVNULL when verbose=False. stderr is always captured so it can be included in any RuntimeError. The return type is now None since no callers used the returned string.

[Copilot]

cache_dir is set to build_ctx.artifact_dir, which will mix Zig’s cache contents with the user-visible build artifacts (e.g., program.helios.o / program.selene.x) and can bloat that directory unexpectedly. Consider using a dedicated subdirectory (e.g., artifact_dir / "zig-cache") and ensure it exists before invoking Zig.

[jake-arkinstall]

@copilot apply changes based on this feedback

[Copilot]

Fixed in commit f6edf63. All five invoke_zig call sites in helios.py and selene.py now use artifact_dir / "zig-cache" as the dedicated cache subdirectory, with mkdir(exist_ok=True) called before each invocation to ensure it exists.