snap tests are completely broken

See https://gitlab.com/freedesktop-sdk/freedesktop-sdk/-/jobs/2609900132

Our snap apps are failing test snap.v2_security:security-snap-v2:squashfs_repack_checksum: (ERROR) checksums do not match. Please ensure the snap is created with either 'snapcraft pack <DIR>' (using snapcraft >= 2.38) or 'mksquashfs <dir> <snap> -noappend -comp xz -all-root -no-xattrs -no-fragments'. If using electron-builder, please upgrade to latest stable (>= 20.14.7). See https://forum.snapcraft.io/t/automated-reviews-and-snapcraft-2-38/4982/17 for details. This prevents publishing anything to our internal ostree repo.