[Windows] Switch to 'PURE' bridging mode for now
With newer llvm, importing 'llvm/include/llvm/ADT/DynamicAPInt.h' causes
an error:
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.39.33519\include\numeric:598:12: error: function '_Select_countr_zero_impl<unsigned long long, (lambda at C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.39.33519\include\numeric:598:55)>' with deduced return type cannot be used before it is defined
