Require LLVM 19 for llvm_storage on aarch64

[AntonOresten]

Closes #113

-(::BFloat16) gives an LLVM error on 1.12 only: 1.11 uses LLVM 16, 1.12 uses 18, and 1.13 uses 20. This PR changes the requirement for LLVM storage on aarch64. The reason this wasn't detected by CI is that the run was on Oct 6, 1.12 was released on Oct 8, and CI only tests nightly on Ubuntu and Windows.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.01%. Comparing base (bd1ff36) to head (bc98c6e).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #117   +/-   ##
=======================================
  Coverage   97.01%   97.01%           
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  Files           3        3           
  Lines         201      201           
=======================================
  Hits          195      195           
  Misses          6        6           

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[AntonOresten]

Per the README:

Support for 64-bit ARM processors (aarch64) is is available with Julia 1.12 which uses LLVM 19.

It seems Julia 1.12 is actually using LLVM 18, and I just realized even LLVM 19 might be optimistic. The safest choice would be to require LLVM 20, but not sure if anyone is building Julia with LLVM 19. If they said it would work on LLVM 19, but 1.12 just happens to not have it, then it probably would.

I suppose #77 should've required LLVM 19 for llvm_storage as well, not just llvm_arithmetic.

One could rerun the CI on master before merging to verify the error on Julia 1 - macos-latest - aarch64.

[AntonOresten]

@maleadt could you have a look when you get the chance?

[maleadt]

That's annoying. IIRC I did verify this, maybe only using Compiler Explorer, but still. I don't have time to investigate in detail, so I'll trust your analysis on this.