I know Martin finds something like this useful for testing sstate signatures,
this adds one to meta-selftest so we can use it from oe-selftest in the sstate
tests there too.
(From OE-Core rev: 7ed3364b7ca61b210fce5ed014ab700e24ee470b)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>