[llvm] [LLVM][Clang][AArch64] Implement AArch64 build attributes (PR #123990)

[Hans Wennborg via llvm-commits]

zmodem wrote:

Specifically it seems like the `.ARM.attributes` sections are accumulating in the linked output: https://crbug.com/394238798#comment6 

>From looking briefly at the linked spec, it sounds like the attributes are supposed to go in the relocatable object files, not that they should be linked into the executables.

@smithp35 in case I'm not getting this right.

https://github.com/llvm/llvm-project/pull/123990