Enable AArch64 arithmetic on LLVM 19.

[maleadt]

x-ref JuliaLang/julia#55486 (comment)

Draft until we can test this, i.e., when there's a LLVM 19 PR on the Julia repository.
Version bound determined by building LLVM 19 locally, using: https://godbolt.org/z/7oGoMWrax

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.74%. Comparing base (2266cc5) to head (fba12ad).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #77   +/-   ##
=======================================
  Coverage   65.74%   65.74%           
=======================================
  Files           3        3           
  Lines         181      181           
=======================================
  Hits          119      119           
  Misses         62       62           

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[maleadt]

I built Julia against LLVM 19, JuliaLang/julia#55486 (comment), and everything seems to work fine. So let's go ahead and merge this.

Julia Version 1.12.0-DEV.1047
Commit 3c4cc92d88* (2024-08-14 06:12 UTC)
Platform Info:
  OS: macOS (arm64-apple-darwin23.6.0)
  CPU: 11 × Apple M3 Pro
  WORD_SIZE: 64
  LLVM: libLLVM-19.1.0 (ORCJIT, apple-m3)
Threads: 1 default, 0 interactive, 1 GC (on 5 virtual cores)
Environment:
  JULIA_PKG_SERVER_REGISTRY_PREFERENCE = eager
  JULIA_PKG_USE_CLI_GIT = true
  JULIA_PKG_DEVDIR = /Users/tim/Julia/pkg

┌ Info: Testing BFloat16s
│   BFloat16s.llvm_storage = true
└   BFloat16s.llvm_arithmetic = true
Test Summary: | Pass  Total  Time
comparisons   |   17     17  0.0s
Test Summary: | Pass  Total  Time
conversions   |    4      4  0.0s
Test Summary: | Pass  Total  Time
abi           |    2      2  0.0s
Test Summary: | Pass  Total  Time
functions     |    8      8  0.0s
Test Summary: | Pass  Total  Time
arithmetic    |    6      6  0.0s
Test Summary: | Pass  Total  Time
printf        |   23     23  0.2s
Test Summary: | Pass  Total  Time
random        |    6      6  0.1s
Test Summary: | Pass  Total  Time
round         |    1      1  0.0s
Test Summary:  | Pass  Total  Time
Next/prevfloat |   15     15  0.0s
Test Summary:      | Pass  Total  Time
Decompose BFloat16 |  100    100  0.0s
Test Summary:               | Pass  Total  Time
Next/prevfloat(x,::Integer) |    9      9  0.0s
Test Summary: | Pass  Total  Time
maxintfloat   |    2      2  0.0s
Test Summary: | Pass  Total  Time
BFloat16 bits |    3      3  0.0s
Test Summary:  | Pass  Total  Time
BFloat16 parts |    9      9  0.0s
     Testing BFloat16s tests passed