[llvm] [AArch64][Build Attributes] Improve Parsing and Formatting (PR #126530)

[Oliver Stannard via llvm-commits]

https://github.com/ostannard commented:

When splitting patches up, please make sure that the tests are updated in the same patch which makes the functional change. This makes it much easier for the reviewer to see what has/hasn't been tested, and the tests are also useful to the reviewer as an example of what behaviour is changed/added by the patch. In the current version of this PR, you've deleted most of the tests in the first commit and re-added them in the last one, which makes it harder to see what has been added/changed in them.

https://github.com/llvm/llvm-project/pull/126530