[BUG] Does not build with clang-cl

**Describe the bug**
Due to adding the /MP option to MSVC like compilers, benchmark doesn't build on clang-cl or icx-cl as they don't handle it in any way, and will throw an unused command line option warning. Due to -Werror this will cause the compilation to fail. 

**System**
Which OS, compiler, and compiler version are you using:
  - OS: Windows 11
  - Compiler and version: Clang-cl 19

**To reproduce**
Steps to reproduce the behavior:
1. sync to commit ... master
2.  cmake -Bbuild -GNinja -DCMAKE_BUILD_TYPE=Release -DCMAKE_LINKER=lld-link -DCMAKE_C_COMPILER=clang-cl -DCMAKE_CXX_COMPILER=clang-cl
3. cmake --build build
4. See error

**Expected behavior**
Builds with no modification to cmakelists (removing MP solves it). 
The solution would be checking if it is clang, and if so omitting /MP. Not sure how to check for icx. 

**Screenshots**
![Image](https://github.com/user-attachments/assets/b67840a4-2724-4b19-beed-22d0ec5d7dbf)


**Additional context**
Also should affect icx-cl, as it is based on clang. 

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