There were two problems:
- Writing the date on Windows used the wrong syntax. In Powershell,
env variables are addressed as $env:NAME, not $NAME.
- Use different caches for opt vs fastbuild. We are currently using
opt caches for fastbuilds, which results in lots of cache misses.
Uses a bazel --disk_cache to cache build outputs between builds. Bazel
also has a local cache, e.g. in ~/.cache/bazel/_bazel_$USER/cache, but
that one can't be used as it won't reuse data across checkouts. A disk
cache is like a remote cache, except that it's on the local disk.
Github first looks for a cache with the given exact key in the current
branch, then in the main branch. If there's a cache hit, the cache
isn't updated (they're read-only!). To prevent that caches become
stale, they are timestamped using the current year and month, so that
the cache is force-renewed every month. Bazel disk caches also just
grow, so this technique prevents that the cache grows indefinitely,
eventually causing cache trashing.
* Add a Github action for building and testing
On Windows, -- -//third_party/... doesn't seem to work, so add all test directories manually. Also run the tests_*. We run only fastbuild tests here, since the opt tests will be run in the release workflow.
Also fix a number of compilation and test issues found along the way.
