Cannot Compile Optix SDK Samples, "Cannot open source file"

I really can’t say why this is happening on your machine.
It could still be the older Visual Studio Community edition or the older Windows SDK.

The most similar error I could find is this but that doesn’t have the incorrect characters, it only chokes on the spaces:
https://stackoverflow.com/questions/66116251/error-c1083-how-do-i-fix-my-broken-visual-studio-compiler

Maybe provide the *.vcxproj file of the failing sutil build.

Some other web sites blamed the Windows SDK.
I never used the Visual Studio installer to install Windows SDKs.
The Windows SDK comes with its own installer:
https://developer.microsoft.com/en-us/windows/downloads/windows-sdk/

Do other CMake projects work on your system?

You could try if you can get my OptiX examples to work. github link here:
https://forums.developer.nvidia.com/t/optix-advanced-samples-on-github/48410/4
I’m only using the OptiX SDK headers in a different application framework, so neither the OptiX SDK’s FindCUDA.cmake nor any other of its scripts or helpers.

Sidenote: CMake deprecated its own FindCUDA.cmake in version 3.10 and has finally hidden it in version 3.27!
https://cmake.org/cmake/help/latest/module/FindCUDA.html
It has been replaced with FindCUDAToolkit.cmake, respectively CMake’s native LANGUAGE CUDA feature.
Latter requires a separate CMake “Object Library” project to isolate the OptiX device code translation to PTX or OptiX-IR from native CUDA objects.
Described here: https://forums.developer.nvidia.com/t/why-am-i-getting-optix-dir-notfound/279085/4