We need to be able to update uninative if the version changes. To do this,
stash a checksum of the installed uninative tarball into a file. If this
changes, we update uninative.
For cleaner download messages, we place the tarballs into directories
based on the checksum.
(From OE-Core rev: f767f94295032792d84fd323bffee137a6467e01)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>