[clang] [llvm] [LLVM][Clang][AArch64] Implement AArch64 build attributes (PR #118771)

[Oliver Stannard via llvm-commits]

https://github.com/ostannard commented:

It looks like this is still missing the ability to emit build attributes by number, for future attributes the assembler does not know about.

There is also still a lot of new code here not covered by tests:
* Tests for pauthabi platform/version in codegen
* Tests for assembly parser errors
* Tests for attributes with NTBS values

https://github.com/llvm/llvm-project/pull/118771