Share cache with local container

[kalikiana]

@sergiusens

An overview of the cache strategy was done and we came to the agreement we only want to do this for local remotes.

In the case of a local LXD container, snapcraft’s cache should be mounted into the container.

[sergiusens]

the other constraint is that the base would need to match or we would need to update the caching to consider multiple bases.