selftests: add tests for INCOMPATIBLE_LICENSE
One bug went unnoticed without these selftests: an INCOMPATIBLE_LICENSE
with a non-SPDX license for a package with that non-SPDX license wasn't
enforcing the denial of build for said package. See
4b6ce4604cc15e289a48f8586d58a101b7a70b52 ("meta: license: fix non-SPDX
license being removed from INCOMPATIBLE_LICENSE")
While adding a test for that particular case, let's add a few more so
that we cover a handful more use cases of INCOMPATIBLE_LICENSE.
Signed-off-by: Quentin Schulz <quentin.schulz@streamunlimited.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
