[llvm] Support: unlock Windows API support, switch to Windows 10 RS1+ APIs (PR #102240)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

> This API was introduced with Windows 10 RS1, and although there are LTSC contracts that allow older versions to be supported still, the mainstream support system has declared this release to be obsoleted. As such, assuming that the OS is at least as new as this is reasonable.

If we'd go this way, we should update the docs that state our minimum required target. But I would want to object to bumping the requirement that far - within the msys2 project, they still support older versions (CC @lazka @mati865 @jeremyd2019) as far as I know, and likewise llvm-mingw also supports running the toolchain on Windows 7.

In this case, it should be fairly straightforward to change this to try using the new `FileRenameInfoEx`, and if it fails (because running on an older OS that doesn't support it) fall back on the existing code with `FileRenameInfo` - I tested amending your patch to do that.

https://github.com/llvm/llvm-project/pull/102240