Add ability to get updated Z3 build for Everest Nightly

Some more details on how we would like to proceed... first of all, the reason we're doing this is because many improvements lurk in the nightly version of z3, and now that we have very good CI, we can confidently update z3 without being afraid of breaking the universe.

The process would be as follows (in order):

[x] put a copy of the z3 binary that we want in FStarLang/binaries@master, named, say,z3-hash-platform.{zip,tar.gz}
[x] make the everest script track the z3 hash that we want, and make it capable of downloading, unzipping, and adding z3 to the PATH for all platforms, via the everest pull command -- sub-steps: probably a z3_version file in the everest repository (under version control), a z3 subfolder in everest where we unzip the binaries, and a check in the everest script that the z3 binary we have matches what is in the z3_version file
[x] change the Dockerfile to no longer install z3 manually, but instead rely on everest check to do the right thing
[ ] add a weekly task (using cygwin's cron, perhaps?), to run everest pull weekly, so that the windows environment of the build machine can get the latest z3 version updated all the time
[x] this means, among other things, that everest should put z3 in the same PATH all the time (so that we don't have to update the Windows machine's system PATH all the time)
[ ] next, add a new build definition, just like everest-upgrade-windows, that is called everest-z3 upgrade-windows... this would be a project-everest/everest build job, and it would fetch the latest z3 binary from https://github.com/Z3Prover/bin, and run ./everest pull, then replace the existing z3 with the latest one, then ./everest verify, and if everything works out, refresh z3_version, commit and push
[ ] in addition to that, because z3 keeps their binaries for a day only, and we intend to run this only every week, we need to refresh the FStarLang/bin repository to store this week's z3 binaries. Among many possible solutions, one way to achieve that is (sketch):

git clone git@github.com:FStarLang/binaries
cd binaries
git rm *.zip
for platform in $z3_platforms; do
  wget https://github.com/Z3Prover/bin/raw/master/nightly/z3-$Z3_VERSION_HASH-$platform.zip
  git add z3-$Z3_VERSION_HASH-$platform.zip
done
git commit -a --amend -m "Replacing z3 binaries with new good ones"
git push -f origin master

Note the use of git push -f which overrides the existing commit with a fresh one, hence guaranteeing that we don't keep every single z3 version we ever checked in in the repository's history.

Happy to provide any further answers on the process... it's a long one but fortunately we can break it down in many smaller sub-steps!

Cheers,

Jonathan

project-everest / everest-ci

Add ability to get updated Z3 build for Everest Nightly #85