CI test matrix verilator cache fail on new branches

[howardtr]

This was recently pushed to dev-public: 51be55d#diff-81f00368f6e2ec134dea48176d97d18019089c9677b783b531d7e669e8828289

I merged this into dev-goog and ran into an issue: Latest run

The verilator step that saves the installed directory is failing to save the cache:

Run actions/cache/save@v3
/usr/bin/tar --posix -cf cache.tzst --exclude cache.tzst -P -C /home/runner/work/caliptra-rtl/caliptra-rtl --files-from manifest.txt --use-compress-program zstdmt
Failed to save: Unable to reserve cache with key verilator-v5.002-f3e6951f0c1d, another job may be creating this cache. More details: Cache already exists. Scope: refs/heads/dev-goog, Key: verilator-v5.002-f3e6951f0c1d, Version: d8d92e0975f28a87cab73a7e22924eff0986e9d4648d3eac429d79abece1e6f7
Warning: Cache save failed.

It's certainly in the right direction, but it looks like we need to move the installation of verilator prior to the matrix generation since the caches seem to be clobbering each other in a branch that is running the CI for the first time

I'll take a quick look at this to unblock development at least on the dev-goog branch

[howardtr]

I added a build_tool stage prior to the matrix generation here: #70

I'm now running into an issue where it seems top of tree is broken. Filed #71