[clang] [clang] [ARM] Explicitly enable NEON for Windows/Darwin targets (PR #122095)

[David Spickett via cfe-commits]

DavidSpickett wrote:

Setting default features for a platform based on what we happened to choose (likely with a very thin justification) to be the default CPU sounds fragile to me, so I think this patch is a good step forward. Even if there weren't this downstream patch interacting with it, I think it would be a good change to make.

> This obviously is a downstream issue - but I'm trying to make it more explicit upstream, to make it easier for the downstreams that do patch it.

I wouldn't have expected the Debian patch to have these consequences either, so I agree with doing this.

https://github.com/llvm/llvm-project/pull/122095