Basically, its probably simplest to tar up the ivy cache dir after a green CI and push that somewhere, pulling it down on the front-end of a CI run:

$ ./pants options --scope=ivy --name=cache_dir
ivy.cache_dir = /home/jsirois/.ivy2/pants (from HARDCODED)

This assumes you use the option above to point pants to a workspace-local

--ivy-cache-dir

to avoid concurrency issues.