test i686 and s390x on CI

[folkertdev]

fixes #134

by just ignoring those tests. The error is not a real error in that we produce something different form zlib(-ng) on those platforms, but our output is still valid.

On CI, I can't get the cross-compilation of zlib-ng to work, but I did run this locally (where cross-compilation does work?!) . We now test the zlib-rs crate on i686 and s390x, so real logic errors should be caught by that. I'll give cross-compiling zlib-ng another go at a later point.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.25%. Comparing base (0cfb39d) to head (8cfb75f).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #139      +/-   ##
==========================================
+ Coverage   91.23%   91.25%   +0.02%     
==========================================
  Files          41       41              
  Lines       13181    13200      +19     
==========================================
+ Hits        12026    12046      +20     
+ Misses       1155     1154       -1     

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