this allows disabling autopkgtests for certain architectures (or limiting them to a certain subset) to workaround slow runners or other arch-related problems.
the value is transitive (like test_is_broken), with an empty list serving as "reset value" to mark a certain PkgFeature test as having no Architecture restrictons.
Signed-off-by: Fabian Grünbichler debian@fabian.gruenbichler.email