Use default arch in CI

[JoshuaLampert]

There are warnings (e.g., https://github.com/trixi-framework/P4est.jl/actions/runs/12108765313) in the CI runs because we request x64 on a macOS runner with arm64. I propose to simply use the default architecture, i.e. to remove the arch argument.

[JoshuaLampert]

Oh, macos-latest (macos-14) doesn't run on Julia v1.6. What's the best way to proceed?

1. Use macos-13
2. Exclude macos-latest for Julia v1.6 (and include macos-13 for Julia v1.6)
3. Drop support for Julia v1.6 and Julia v1.7
4. Something else

See also https://discourse.julialang.org/t/how-to-fix-github-actions-ci-failures-with-julia-1-6-or-1-7-on-macos-latest-and-macos-14/117019. I would prefer option 2, but have no strong opinion.

[ranocha]

Option 2 sounds good to me 👍

[ranocha]

https://github.com/trixi-framework/P4est.jl/actions/runs/12126603254/job/33809069600?pr=135 fails

[JoshuaLampert]

Should be fixed now.

[ranocha]

Thanks!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 17.51%. Comparing base (c8d680f) to head (468f7be).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #135   +/-   ##
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  Coverage   17.51%   17.51%           
=======================================
  Files           3        3           
  Lines        1422     1422           
=======================================
  Hits          249      249           
  Misses       1173     1173           

Flag	Coverage Δ
unittests	17.51% <ø> (ø)

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