Update sources added by craft-archives

[mr-cal]

What needs to get done

#150 sets architectures for sources in /etc/apt/sources.list.d/ubuntu.sources.

It doesn't set architectures for other repositories added by craft-archives in /etc/apt/sources.list.d/craft-*.sources.

For example, consider the following project file snippet:

platforms:
  riscv64:
    build-on: [amd64]
    build-for: [riscv64]

package-repositories:
  - type: apt
    # architectures: [amd64] - won't this solve the problem?
    formats: [deb]
    components: [main]
    suites: [noble]
    key-id: F23C5A6CF475977595C89F51BA6932366A755776
    url: https://ppa.launchpadcontent.net/deadsnakes/ppa/ubuntu

  - type: apt
    architectures: [riscv64]
    formats: [deb, deb-src]
    components: [main]
    suites: [noble, noble-updates, noble-backports]
    key-id: F6ECB3762474EDA9D21B7022871920D1991BC93C
    url: http://ports.ubuntu.com/ubuntu-ports

Why it needs to get done

To support cross-compiling in *craft applications.

[syncronize-issues-to-jira]

Thank you for reporting your feedback to us!

The internal ticket has been created: https://warthogs.atlassian.net/browse/CRAFT-4112.

This message was autogenerated

[mr-cal]

@tigarmo - this is the follow-up task we talked about on Monday. I'm not sure if I understand the nuance of the problem, but this is my best guess. Let me know what you think.