Some architectures vary OLDEST_KERNEL and this shouldn't change the allarch
signatures but in current OE-Core can/does. Add differing values to the
test configs to ensure we catch this in future (we want to keep a 32 and
64 bit machine here to test that as well).
(From OE-Core rev: 151ce55ec8ebc91b83bf0d09b9196f11646df1f1)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>