fix(compile): register #8128's optnone knob as a build-cache input

[proggeramlug]

cargo-test — a required context — is red on main right now.

these codegen env vars key neither the build cache nor an exclusion (#6394's rule):
  ["PERRY_LL_RS4GC_OPTNONE_INSTRS"]

Reproduced on main @ 8b1b4b909, so this is not any open PR's doing. It surfaced while I was triaging #8084's red cargo-test, which turns out to be inheriting this.

Cause

#8128 added the knob. Its description says it was "registered as a build-cache key per #6394" — it was not.

Why BUILD_CACHE_ENV_VARS and not an exclusion

The knob stamps optnone+noinline on any function past its instruction threshold, so flipping it skips the middle-end for that function and changes emitted code. An exclusion asserts the opposite — that a variable cannot change emitted code — so the exclusion list would be the wrong home and would re-break the invariant #6394 exists to hold. Without the entry, changing the threshold leaves the build-level no-op check reporting a match and handing back the previous build's executable.

Verification

• Failing on main before the change, passing after.
• cargo test -p perry --bin perry green.
• The test that caught it is the discriminating one: it enumerates codegen env vars and requires each to key the cache or carry a written exclusion, so it goes red again if a future knob skips registration.

Note this class is invisible to cargo test -p perry --lib — perry has no lib target, so the test only runs under --bin perry.

Summary by CodeRabbit

• Bug Fixes
  • Build results now refresh correctly when the garbage-collection optimization setting changes, preventing stale cached builds.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 2b3093c2-9cd8-418e-a3b1-985b9bafc372

📥 Commits

Reviewing files that changed from the base of the PR and between 8b1b4b9 and 2cf1a10.

📒 Files selected for processing (1)

• crates/perry/src/commands/compile/build_cache.rs

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📝 Walkthrough

Walkthrough

The build cache input list now includes PERRY_LL_RS4GC_OPTNONE_INSTRS. Changes to this environment variable invalidate build-level cache hits.

Changes

Build cache invalidation

Layer / File(s)	Summary
Track RS4GC threshold changes crates/perry/src/commands/compile/build_cache.rs	The build cache tracks PERRY_LL_RS4GC_OPTNONE_INSTRS changes. This invalidates cached builds when the RS4GC optnone/noinline instruction threshold changes.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Possibly related PRs

• PerryTS/perry#6855: Updates build-cache invalidation for code-generation environment variables.

Suggested reviewers: jdalton

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/8128-optnone-knob-build-cache

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