We don't need to worry about setting an external directory for the cache because renv 0.15.0 does this by default.
renv now uses an external library by default for R package projects, with the library located within tools::R_user_dir("renv", "cache"). This directory can be configured via the RENV_PATHS_LIBRARY_ROOT environment variable if desired. See vignette("packages", package = "renv") for more details. (#384)
We don't need to worry about setting an external directory for the cache because renv 0.15.0 does this by default.