Support RUNNER_TOOL_CACHE for caching the cosign binary #183
Description
Description
When using self-hosted runners it is common to want to limit network access of github runners (networking costs, workflow speed, air-gap). Github SDK-s provide a mechanism to cache tools in a well known filesystem path (eg. $RUNNER_TOOL_CACHE) allowing re-use of the downloaded binary across job executions as well as allowing for the runner administrator to pre-populate the cache.
It would be great if cosign-installer would also utilize $RUNNER_TOOL_CACHE
#140 is somewhat related.