Add missing / Avoids potential problem of it not seeing an existing cache, depending on the CWD on the cache drive at the point the target is running (which could be anything really).

Turned on use of cache for all platform builds (unless over-ridden by the particular job properties of course).

Bug 1661: Simplified the sequence of pulls/clones via the cache, so the changes simply go from source -> cache -> destination. Made use of --uncompressed flag to speed things up. Including setting the flag when we create a cache entry.