[clang][lld] Increase the default segment alignment from 4k to 64k for windows 64bit binaries (at least for -gnu targets first)?

I’m working on porting Wine to support running Windows‑on‑ARM binaries on Apple Silicon Macs. One major obstacle is that Apple uses a 16 KB page size, and Android appears to be moving in the same direction. In my experiments, I was able to get binaries running correctly by increasing Clang’s segment alignment from 4 KB to 64 KB. I’ve also successfully ported GCC for Windows‑on‑ARM, though that work hasn’t been merged yet.

Given these trends, it may be time to consider raising the default segment alignment from 4 KB to 64 KB for 64‑bit Windows targets—at least for x86_64‑windows‑gnu and aarch64‑windows‑gnu initially. This would improve forward compatibility for Wine and other environments that may need to support larger page sizes. It would also give Windows itself the flexibility to adopt 16 KB or even 64 KB pages in the future, potentially as a configurable system option.

For MSVC targets, I’ve asked Microsoft developers whether they plan to make a similar change in future versions of the Visual C++ toolchain:
https://developercommunity.visualstudio.com/t/Visual-C-compilers-should-default-segm/11133260

Start by reviewing how Clang and lld currently select segment alignment for x86_64-windows-gnu and aarch64-windows-gnu targets. Determine where the 4 KB default is defined and how existing Windows 64-bit binary tests verify it; done means an agreed implementation and passing coverage for the proposed 64 KB default.

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