Trim CI Failure Policy Discussion

The Trim test group currently fails on CI across macOS, Ubuntu, and Windows with Juliac reporting:
could not find a compiler, looked for gcc and clang

This raises a question: should missing compiler be treated as a skip condition, or as a hard failure?

Why

• Trim is validating executable compilation behavior, not just runtime correctness.
• Skipping on missing compiler can hide real breakage in CI setup.
• A failing preflight gives faster, actionable signal to maintainers.

Suggested Approach

• Add a compiler preflight for Trim jobs and fail early with a clear message if no compiler is available.
• Define at least one required canonical Trim target (e.g., Linux x64 with pinned toolchain).
• Keep broader cross-platform Trim coverage as optional/non-blocking until toolchain provisioning is stable on all runners.

Open Questions

• Which Trim target(s) should be required for merge gating?
• Should non-canonical OS Trim jobs remain required, optional, or temporarily disabled?
• Do we want explicit compiler pinning in CI, or rely on runner defaults + preflight checks?