Implement CMake changes to fix building oneAPI in Windows

Description

• Is this a new feature or a bug fix?: fix
• Why these changes are necessary: enable building oneapi in windows
• New functions and their functionality: None
• Can this PR be backported to older versions?: unsure
• Future changes not implemented in this PR: possible fixes for using the Visual Studio Generator with the Intel Toolchains

Fixes: #3609

Changes:

1. Made linking against MKL_SYCL Public in CMake only when building on Windows.
2. Forced CMAKE_MSVC_RUNTIME_LIBRARY="" and added manually the correct MSVC Runtime Library compile flag
   (-MT/MD/MTd/MDd) for the icx when building oneAPI
3. Forced to use the SYCL OpenCL library from oneAPI when building the oneAPI backend.

Consequences:

Using the Intel oneAPI DPC++ Compiler Reference as a baseline, the correct way to build the oneAPI backend in windows is as follows (using MSVC2022 and oneapi 2025 for example):

1. Open command prompt (cmd.exe) or powershell.
2. Initialize oneAPI's environment variables
   In command prompt use:

C:\Program Files (x86)\Intel\oneAPI\setvars.bat

In powershell use

cmd.exe "/K" '"C:\Program Files (x86)\Intel\oneAPI\setvars.bat" && powershell'  

3. Initialize Windows MSVC Compiler Environment Variables
   In command prompt use:

C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvars64.bat

In powershell use:

 cmd.exe "/K" '"C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvars64.bat" && powershell'  

5. CMake configure project using the Ninja generator with the C and C++ compilers set to cl and the SYCL compiler set to icx:

cmake -B build -DCMAKE_C_COMPILER=cl -DCMAKE_CXX_COMPILER=cl -DCMAKE_SYCL_COMPILER=icx -DAF_BUILD_ONEAPI=ON -G Ninja :: ... other options ...

6. CMake build project like normal:

cmake --build build --target afoneapi -j 4

(From testing it seems that the icx compiler tends to use a lot of memory and crash if there are lots of jobs being executed. I recommend -j 4 for an 8-core machine specifically for building the afoneapi target. Furthermore, the linking step for afoneapi.lib takes a significant amount of time).

Changes to Users

• Additional options added to the build: None
• What changes will existing users have to make to their code or build steps?: Yes on windows: see Consequences above

Checklist

• Rebased on latest master
• Code compiles
• Tests pass
• Functions added to unified API
• Functions documented