Add lookup for s390x qemu as well

[okurz]

Related progress issue: https://progress.opensuse.org/issues/158985

[github-actions]

Great PR! Please pay attention to the following items before merging:

Files matching backend/**.pm:

• Consider running manual verification tests, especially for non-qemu backends

This is an automatically generated QA checklist based on modified files.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.43%. Comparing base (e11bad8) to head (793ef8e).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2488   +/-   ##
=======================================
  Coverage   95.43%   95.43%           
=======================================
  Files         149      149           
  Lines       15866    15866           
=======================================
  Hits        15142    15142           
  Misses        724      724           

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