[llvm] [Support] [Windows] Conditionally compile the SetThreadInformation calls (PR #151388)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

> > This API is also hidden if building with MS WinSDK if targeting versions before Windows 10.
> 
> makes me wonder if we want to declare/define these defines/struct if not provided by the windows headers? it would allow the use of EcoQoS no matter how llvm is built

Yes, certainly. Although in practice, I would think most people building with WinSDK end up using the default target version. I think many of those intentionally targeting older versions may be using mingw, where these declarations aren't hidden based on version anyway. (Although that can of course change in the future.) The degradation for those building in that configuration should be quite graceful (behaving like it did before).

Although if you feel strongly about it, I guess you can propose such a patch as well, but it requires a bit more testing, so I'd at least like to land this first, to unbreak @Sharjeel-Khan's builds.

https://github.com/llvm/llvm-project/pull/151388