Currently it seems if master branch doesn't build for 1-2 days then the
cached ESP-IDF install (1.6GB) and Zephyr workspace (3.1GB) caches expire.
Then each PR branch has to create its own redundant cache instead of
falling back to the default branch cache, which is expensive and quickly
blows our 10GB cache limit.
Currently this is mitigated (and possibly happens more frequently) due to
GitHub's relatively soft enforcement of the limit (at time of writing we're
using 33GB of 10GB), but apparently they're going to start enforcing it
more aggressively in October.
(We may find we need to do this twice a day...)
This work was funded through GitHub Sponsors.
Signed-off-by: Angus Gratton <angus@redyak.com.au>
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