Temporarily disable GPU in Windows CI build

[Lestropie]

The Windows build CI check is currently broken with the following message:

FAILED: [code=1] bin/libmrtrix-core.dll cpp/core/libmrtrix-core.dll.a 
C:\Windows\system32\cmd.exe /C "cd . && C:\msys64\ucrt64\bin\c++.exe -O3 -DNDEBUG  -shared -o bin\libmrtrix-core.dll -Wl,--out-implib,cpp\core\libmrtrix-core.dll.a -Wl,--major-image-version,0,--minor-image-version,0 @CMakeFiles\mrtrix-core.rsp && C:\Windows\system32\cmd.exe /C "cd /D D:\a\mrtrix3\mrtrix3\build\cpp\core && C:\msys64\ucrt64\bin\cmake.exe -E copy_if_different D:/a/mrtrix3/mrtrix3/build/_deps/dawn-src/lib/libwebgpu_dawn.a D:/a/mrtrix3/mrtrix3/build/_deps/slang-src/bin/slang-compiler.dll D:/a/mrtrix3/mrtrix3/build/bin""
C:/msys64/ucrt64/bin/../lib/gcc/x86_64-w64-mingw32/16.1.0/../../../../x86_64-w64-mingw32/bin/ld.exe: _deps/dawn-src/lib/libwebgpu_dawn.a(EventManager.cpp.obj):EventManager.cpp:(.rdata$.refptr.__emutls_v._ZSt11__once_call[.refptr.__emutls_v._ZSt11__once_call]+0x0): undefined reference to `__emutls_v._ZSt11__once_call'
C:/msys64/ucrt64/bin/../lib/gcc/x86_64-w64-mingw32/16.1.0/../../../../x86_64-w64-mingw32/bin/ld.exe: _deps/dawn-src/lib/libwebgpu_dawn.a(EventManager.cpp.obj):EventManager.cpp:(.rdata$.refptr.__emutls_v._ZSt15__once_callable[.refptr.__emutls_v._ZSt15__once_callable]+0x0): undefined reference to `__emutls_v._ZSt15__once_callable'
collect2.exe: error: ld returned 1 exit status

This occurs due to a change from GCC15 to GCC16. Specifically the TLS implementation in libstdc++ changes from emulated to native. However the pre-compiled Dawn library does not reflect this. It therefore can't be rectified using the -fno-emulated-tls compiler flag.

Here the proposal is to temporarily disable the building of GPU capabilities in the Windows CI check, in order for merges to dev to pass checks. In time I think we will need to build and package this library a second time for this different compiler version, and have cmake appropriately choose which of them is the correct download. This might take a moment to get right.

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"