On self-hosted runners it can happen that an action (docker container) is cached, resulting in aborting this script because the know_hosts file already exists.
This if clause fixes it.
Setting permissions is intentionally outside the if clause because in all cases we want to reset perms.
On self-hosted runners it can happen that an action (docker container) is cached. This leads to the script trying to create the .ssh dir despite it already existing. The action then fails.
Steven