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

[Tim Blechmann via llvm-commits]

timblechmann 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

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