cache: Include the mock configuration file in the package hash

Signed-off-by: Euan Harris <euan.harris@citrix.com>
cache: Move build outputs into a subdirectory to make way for cache metadata

Signed-off-by: Euan Harris <euan.harris@citrix.com>
cache: Make it easier to identify our temporary directories

Signed-off-by: Euan Harris <euan.harris@citrix.com>