Update it for the new layout of sstate-cache.
Note: It doesn't handle the old sstate-cache/sstate-xxx.tgz (or
siginfo), the user should remove it manually (rm -fr
sstate-cache/sstate-* would be OK).
[YOCTO #2897]
(From OE-Core rev: fcb61aa552a641faafdf2216fa57ba5ac6b9991f)
Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>