snapcraft download debian package from incorrect arch

[Aristo Chen]

Hi,

I am using snapcraft 7.3.1 revision 8931 to build a gadget snap on a focal vagrant environment, and here is the snapcraft.yaml

"""
name: test-gadget
base: core22
version: 22-0.1
summary: test
description: |
  test only
type: gadget
architectures:
  - build-on: amd64
    build-for: arm64
confinement: strict
grade: stable

package-repositories:
  - type: apt
    architectures: [ arm64 ]
    components: [ main ]
    suites: [ jammy, jammy-security, jammy-updates, jammy-backports ]
    key-id: F6ECB3762474EDA9D21B7022871920D1991BC93C
    url: http://ports.ubuntu.com/ubuntu-ports

parts:
  prepare-device-deps:
    plugin: nil
    stage-packages:
      - bsdmainutils:arm64
    stage:
      - usr/bin/hexdump
"""

After the snap is built successfully, it turns out that the bsdmainutils downloaded is actually from amd64 instead of arm64.

I have done some investigation and come up with two potential solution
1. the python-apt somehow return a amd64 package name in "get_providing_packages()" in "python-apt/apt/cache.py", so maybe we can try to check the arch before return the list. However, the "mark_packages()" in "craft_parts/packages/apt_cache.py" will also need to check the length of returned list first instead of accessing the first element directly

2. maybe check the arch in the "mark_packages()" in "craft_parts/packages/apt_cache.py"

Please let me know if you need any further info from me, any suggestions for how to fix is very welcome, and I am happy to try to provide fix with PR as well if there is a plan on how to fix