Function upgrade_cache_dir 

pub fn upgrade_cache_dir() -> Result<PathBuf>

Return the shared upgrade cache directory, creating it on demand.

The path is {data_dir}/upgrades/ where data_dir comes from directories::ProjectDirs (e.g. ~/.local/share/ant/upgrades/ on Linux).

Errors

Returns an error if the platform data directory cannot be determined or the directory cannot be created.