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

[Peter Smith via llvm-commits]

smithp35 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.

It should be like the Arm 32-bit case. The linker should merge all of the input sections and then it is the implementation's choice whether to output a single merged attributes section, or not (GNU ld preferred to output the section).

I think the problem here is that no LLD support has been added (yet) to deal with the attributes sections, so as you say they are just being accumulated. A way of fixing this temporarily would be to submit a temporary patch for LLD to delete them, or to make the output in llvm conditional until LLD support is added. 

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