create-spdx-2.2: Add missing variable exclusions

create-spdx-2.2: Add missing variable exclusions

Some variables cause issues with taskhashes and are accounted for in the
output in other ways, or don't affect it. Exclude these to improve the
taskhashes with create-spdx and allow the sstate selftests to work better.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>