Support for sse2neon.h on ARM Linux

[whatoeatoday]

Hi, thank you for the great library!

I’m currently using xxhash on an ARM Linux system running Ubuntu 24.04, and I noticed that the current use of sse2neon.h seems to be limited to macOS ARM targets.

Looking at the source, sse2neon.h appears to be conditionally included only under APPLE or (aarch64 && APPLE).

Could you clarify why sse2neon.h is limited to macOS ARM in xxhash?

To my knowledge, sse2neon.h is platform-independent and works well on generic ARM64 Linux systems with NEON support — including Ubuntu 24.04.

If there’s no technical limitation, would you consider broadening the condition to include general ARM Linux platforms as well?

Thanks again for your great work!

[redspah]

Thanks for making an issue about this. I don't have an ARM machine on hand to test it, but looking at the source code of the original xxhash just removing the check for APPLE should be fine. I made a branch with that change (mr-neon-not-apple-exclusive), could you run the unit tests locally and see if everything looks fine?