ci(nightly): harden local cache fallback
The nightly Release fallback now retries only when compiler diagnostics identify a real CAS or compilation-cache failure. Successful cache setup output and unrelated compiler errors no longer trigger a second build. The local retry also omits an empty settings array safely under macOS Bash 3.2 with set -u.
Leo said, “it feels like you guys always forget about incremental builds and the external SSDs.” This follow-up keeps the warm local cache available while avoiding a false green from retrying an ordinary compile failure.
This branch is stacked on #30107 (ci(nightly): retry local cache after fleet CAS failure) and should land after that PR. Runtime regression coverage exercises both a CAS failure that retries and an unrelated compiler error that remains red.
Validation:
python3 -m unittest tests/test_ci_fleet_compilation_cache.py(8 tests)git diff --check
Agent session: agent session
🤖 Generated with Claude Code