[SECO-SETUP][SSTATE_CACHE] Utilize sstate_cache from CI servers in local builds
CI servers (Hamburg) were configured to store sstate_cache
on a NAS drive, which makes it possible to mount and use it as an sstate_cache
mirror on development Linux servers.
This modifies the local.conf to automatically use the sstate_cache
mirror when it is present on the server.
Edited by Andrii Sosiuk