Fix Ruby dependency caching in jekyll_build job
I thought I set up dependency caching for Ruby in the jekyll_build
job. But every time I go to run a new job without changing Ruby dependencies, it still installs all the packages again instead of pulling from a cache.
There is a chance that I am misreading it and it is "installing" the files from the on-disk cache. But I need a way to validate what is happening in the current environment to determine the correct mitigation.