[clang] [llvm] [AArch64] set AppleA14 architecture version to v8.4-a (PR #92600)

[Jon Roelofs via llvm-commits]

https://github.com/jroelofs approved this pull request.

Correct, apple-m1 does not have BTI, but BTI is required for v8.5. My mistake.

https://github.com/llvm/llvm-project/pull/92600