The macOS job failed to link with '-lopenh264 not found': the bare
ffmpeg-<os>-<arch>- restore-key brought back an FFmpeg built before
openh264 was dropped (982593aa2), and the always() save re-saved that
stale tree under the new key, poisoning every later run. The cache key
now hashes both configure inputs (build-ffmpeg.sh AND install-deps.sh,
whose package set decides the enable_if_pkg probes), and the bare
fallback is gone: a changed configure input costs a rebuild instead of
restoring a mismatched tree. The poisoned macOS cache entries were
deleted.