It's possible only to whitelist architectures. Although, I would like to exclude the ones I really know don't work. E.g. my application works only on little-endian architectures and the only architecture I need to exclude is s390x. Currently I have to specify all architectures except of s390x instead and my package won't even try to build on a new architecture added to snapcraft CI (as recently happened with riscv64). Even better if it will be possible to specify architectures heuristically, like "only little endian".