You could try to change it through the environment variable:
WP_CLI_CACHE_DIR
as we have it included in the WP_CLI::get_cache() method (src):
$dir = getenv( 'WP_CLI_CACHE_DIR' ) ? : "$home/.wp-cli/cache";
You can also check out issue #1848 – Use shared cache directory for multiple installs for usage examples.
In the WP-CLI Handbook on make.wordpress.org, we have a list of environment variables used by WP-CLI.