CI: add omniOS

[ThomasWaldmann]

fixes #9118.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.92%. Comparing base (cf20f8c) to head (627d16a).
⚠️ Report is 15 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9314   +/-   ##
=======================================
  Coverage   75.92%   75.92%           
=======================================
  Files          86       86           
  Lines       14777    14777           
  Branches     2201     2201           
=======================================
  Hits        11220    11220           
  Misses       2880     2880           
  Partials      677      677           

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[ThomasWaldmann]

libxxhash: omniosorg/illumos-omnios#1647

[github-actions]

Backport failed for 1.4-maint, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin 1.4-maint
git worktree add -d .worktree/backport-9314-to-1.4-maint origin/1.4-maint
cd .worktree/backport-9314-to-1.4-maint
git switch --create backport-9314-to-1.4-maint
git cherry-pick -x 627d16ac8074635156e211979d04bd26334a1891