Cache key isolation: Include the build flavour (ccwarn/asan/gcov) in the
build ccache key, so the coverage (gcov), asan, and RTLMeter
(ccwarn-off) configurations no longer share and thrash the single
'<runs-on>-<cc>' bucket, nor warm-start from each other's (near-useless)
caches.
Prune stale entries instead of a fixed size cap: After building/testing,
evict ccache entries this run did not touch (--evict-older-than, based
on the run's own duration). This bounds the saved cache to the current
working set, so CCACHE_MAXSIZE and CCACHE_LIMIT_MULTIPLE are no longer
needed and are removed (ccache falls back to its 5G default ceiling, but
is realistically much smaller).
ccache configuration:
- Drop CCACHE_COMPRESS (already the default in ccache 4.x).
- Add CCACHE_COMPILERCHECK=content, so a changed compiler mtime on a rebuilt
ephemeral runner image does not invalidate the whole restored cache.
- Hoist all ccache-related variables (CACHE_BASE_KEY, CCACHE_*, CXX) to the
workflow-level env.
Remove dead ccache scaffolding:
- reusable-lint-py: the job never compiles or caches; drop its ccache env.
- reusable-rtlmeter-run: remove the disabled persistent-cache step and its
storage variables; keep CCACHE_DISABLE=1, since caching must stay off to
keep RTLMeter timings representative.
Store test job ccache as artifacts for reuse
5750c888a6