feat(ci): Improve the bazel cache optimization (#368)

Bazel cache currently does not fit into the 10GB quota on GitHub.

bin/optimize-bazel-cache.sh

@@ -3,10 +3,16 @@
 # Optimize the size of bazel cache
 #
 
-set -eEuo pipefail
+set -eExuo pipefail
 
 echo "Bazel cache directory contents:"
-ls -l --full-time ~/.cache/bazel || exit 0  # In case bazel cache isn't mounted yet on github, we need to stop here
+ls -l --full-time ~/.cache/bazel || exit 0 # In case bazel cache isn't mounted yet on github, we need to stop here
+
+du -sh --total ~/.cache/bazel/*
+
+bazel clean
 du -sh --total ~/.cache/bazel/*
+
 sudo apt install -qy rdfind
 sudo rdfind -makehardlinks true "$(bazel info output_base | grep .cache | tail -n1)"
+du -sh --total ~/.cache/bazel/*