Follow upstream's disentangling of BUCK caches

In 6f6de0d32cc9b9e1adf65bde3fa0854e6bd26db9, Gerrit moved downloaded
artifacts from

  ~/.gerritcodereview/buck-cache

to

  ~/.gerritcodereview/buck-cache/downloaded-artifacts

. To avoid unnecessarily downloading artifacts, we reflect this move
also for bucklets.
(Note that we do not reflect the above commit's move of the cache for
BUCK built artifacts, as for bucklets builds, those artifacts reside
outside of ~/.gerritcodereview anyways)

Change-Id: I7327ff6c1736f9af8ea15450949dc6a4bc10b684
1 file changed