…torch#159273)

PyTorch with ROCm on Windows is built with clang-cl and not MSVC. This code path is specific to the MSVC compiler so it should be checking for MSC_VER, not just WIN32. The change here is similar to pytorch#146606.

This fixes downstream build errors using clang-cl like https://github.com/ROCm/TheRock/actions/runs/16569646709/job/46858176812 (patched and tested downstream at ROCm/TheRock#1140):
```
[7099/7147] Building CXX object functorch\CMakeFiles\functorch.dir\csrc\dim\dim.cpp.obj
FAILED: functorch/CMakeFiles/functorch.dir/csrc/dim/dim.cpp.obj
C:\home\runner\_work\_tool\Python\3.11.9\x64\Lib\site-packages\_rocm_sdk_devel\lib\llvm\bin\clang-cl.exe  /nologo -TP -DEXPORT_AOTI_FUNCTIONS -DFUNCTORCH_BUILD_MAIN_LIB -DMINIZ_DISABLE_ZIP_READER_CRC32_CHECKS -DNOMINMAX -DONNXIFI_ENABLE_EXT=1 -DONNX_ML=1 -DONNX_NAMESPACE=onnx_torch -DROCM_ON_WINDOWS -DROCM_USE_FLOAT16 -DROCM_VERSION=70000 -DTORCH_API_INCLUDE_EXTENSION_H -DTORCH_EXTENSION_NAME=_C -DTORCH_HIP_VERSION=700 -DUSE_EXTERNAL_MZCRC -DUSE_MIMALLOC -DUSE_PROF_API=1 -DWIN32_LEAN_AND_MEAN -D_CRT_SECURE_NO_DEPRECATE=1 -D_UCRT_LEGACY_INFINITY -D__HIP_PLATFORM_AMD__ -D__HIP_PLATFORM_AMD__=1 -Dfunctorch_EXPORTS -IB:\src\torch\build\aten\src -IB:\src\torch\aten\src -IB:\src\torch\build -IB:\src\torch -IB:\src\torch\nlohmann -IB:\src\torch\moodycamel -IB:\src\torch\third_party\mimalloc\include -IB:\src\torch\functorch -IB:\src\torch\torch\csrc\api -IB:\src\torch\torch\csrc\api\include -IB:\src\torch\c10\.. -IB:\src\torch\c10\hip\..\.. -IB:\src\torch\torch\.. -IB:\src\torch\torch\..\aten\src -IB:\src\torch\torch\..\aten\src\TH -IB:\src\torch\build\caffe2\aten\src -IB:\src\torch\build\third_party -IB:\src\torch\build\third_party\onnx -IB:\src\torch\torch\..\third_party\valgrind-headers -IB:\src\torch\torch\..\third_party\gloo -IB:\src\torch\torch\..\third_party\onnx -IB:\src\torch\torch\..\third_party\flatbuffers\include -IB:\src\torch\torch\..\third_party\kineto\libkineto\include -IB:\src\torch\torch\..\third_party\cpp-httplib -IB:\src\torch\torch\..\third_party\nlohmann\include -IB:\src\torch\torch\csrc -IB:\src\torch\torch\lib -IB:\src\torch\torch\standalone -IB:\src\torch\torch\lib\libshm_windows -imsvcC:\home\runner\_work\_tool\Python\3.11.9\x64\Lib\site-packages\_rocm_sdk_devel\include -imsvcB:\src\torch\third_party\protobuf\src -imsvcB:\src\torch\third_party\XNNPACK\include -imsvcB:\src\torch\third_party\ittapi\include -imsvcB:\src\torch\cmake\..\third_party\eigen -imsvcB:\src\torch\third_party\ideep\mkl-dnn\include\oneapi\dnnl -imsvcB:\src\torch\third_party\ideep\include -imsvcB:\src\torch\INTERFACE -imsvcB:\src\torch\third_party\nlohmann\include -imsvcB:\src\torch\third_party\concurrentqueue -imsvcC:\home\runner\_work\_tool\Python\3.11.9\x64\Lib\site-packages\_rocm_sdk_devel\include\hiprand -imsvcC:\home\runner\_work\_tool\Python\3.11.9\x64\Lib\site-packages\_rocm_sdk_devel\include\rocrand -imsvcB:\src\torch\cmake\..\third_party\pybind11\include -imsvcC:\home\runner\_work\_tool\Python\3.11.9\x64\include /DWIN32 /D_WINDOWS /EHsc /Zc:__cplusplus /bigobj /FS /utf-8 -DUSE_PTHREADPOOL -DNDEBUG -DUSE_FBGEMM -DUSE_XNNPACK -DSYMBOLICATE_MOBILE_DEBUG_HANDLE /wd4624 /wd4068 /wd4067 /wd4267 /wd4661 /wd4717 /wd4244 /wd4804 /wd4273 /O2 /Ob2 /DNDEBUG /bigobj -DNDEBUG -std:c++17 -MD -Z7 -Wmissing-prototypes -Werror=missing-prototypes /permissive- /d2implyavx512upperregs- /EHsc /bigobj -fms-runtime-lib=dll -D__HIP_PLATFORM_AMD__=1 -DCUDA_HAS_FP16=1 -DUSE_ROCM -D__HIP_NO_HALF_OPERATORS__=1 -D__HIP_NO_HALF_CONVERSIONS__=1 -DTORCH_HIP_VERSION=700 -Wno-shift-count-negative -Wno-shift-count-overflow -Wno-duplicate-decl-specifier -DCAFFE2_USE_MIOPEN -DTHRUST_DEVICE_SYSTEM=THRUST_DEVICE_SYSTEM_HIP -std=c++17 -DHIPBLAS_V2 -DHIP_ENABLE_WARP_SYNC_BUILTINS -fms-extensions -Wno-ignored-attributes /showIncludes /Fofunctorch\CMakeFiles\functorch.dir\csrc\dim\dim.cpp.obj /Fdfunctorch\CMakeFiles\functorch.dir\ -c -- B:\src\torch\functorch\csrc\dim\dim.cpp
clang-cl: warning: unknown argument ignored in clang-cl: '-std=c++17' [-Wunknown-argument]
clang-cl: warning: argument unused during compilation: '/d2implyavx512upperregs-' [-Wunused-command-line-argument]
In file included from B:\src\torch\functorch\csrc\dim\dim.cpp:36:
B:\src\torch\functorch\csrc\dim\arena.h(14,21): error: functions that differ only in their return type cannot be overloaded
   14 | inline unsigned int __builtin_clz(unsigned int x) {
      |        ~~~~~~~~~~~~ ^
C:\home\runner\_work\_tool\Python\3.11.9\x64\Lib\site-packages\_rocm_sdk_devel\lib\llvm\lib\clang\20\include\ia32intrin.h(60,15): note: '__builtin_clz' is a builtin with type 'int (unsigned int) noexcept'
   60 |   return 31 - __builtin_clz((unsigned int)__A);
      |               ^
1 error generated.
[7100/7147] Building CXX object caffe2\torch\CMakeFiles\torch_python.dir\csrc\utils\tensor_list.cpp.obj
```

> [!NOTE]
> I haven't been able to reproduce those errors locally, but we have CI jobs that consistently fail when building for Python 3.11 but not 3.12 or 3.13. I'm not sure what is different between those builds, but the code fix seems correct.

There are a few other variations on fixes to this floating around, such as:
* https://github.com/jibsen/blz4/blob/a97a957af0552f64baa9423ce5e08d724a7663c5/lz4.c#L34-L43 (checking with `__has_builtin`)
* https://github.com/ifb/makeDNG/blob/c98c55ec7e96856d2fdeea611acc40480e4b44ed/lj92.c#L31-L46 (the same code as here, but with `_MSC_VER`)
* https://github.com/eugeneyuchunlin/OptimizedQDS/blob/2760e5a2bb2cc9c819ae9c0e5fe9042e24aa1327/def.h#L23-L25 (using `__lzcnt` instead of a custom implementation)

Pull Request resolved: pytorch#159273
Approved by: https://github.com/Skylion007, https://github.com/m-gallus