Purpose of this is to allow us to avoid re-downloading everything
every time we rebuild the chroot.
This maintains two directories; host and target. Future enhancement
involves collapsing this into one- this requires some host work however,
and has some potential gotchas in doing so.
Meanwhile, we now store distfiles in repo/distfiles/{host,target},
and mount bind repo/distfiles into /var/cache/distfiles.
An upgrade script in turn optimistically tries to move the content
into the new location; if it can't complete the move, it wipes the
content and the user has to redownload it (acceptable, if annoying).
BUG=chromium-os:13115
TEST=cbuildbot x86-generic-full
Change-Id: Iea96429df0e1fdc4ac0860fbce0daabc90c4c2a3
Reviewed-on: https://gerrit.chromium.org/gerrit/15189
Reviewed-by: Brian Harring <ferringb@chromium.org>
Tested-by: Brian Harring <ferringb@chromium.org>
Commit-Ready: Brian Harring <ferringb@chromium.org>
