In RAD Studio 12, OpenCV built without errors.
The library is not being built in RAD Studio 13, error:
Error E4974 D:/CMAKE/OpenCV/vtk/ThirdParty/diy2\vtkdiy2/include/vtkdiy2\fmt\core.h 272(30): implicit instantiation of undefined template 'std::char_traitsfmt::char8_t'
272 | : data_(s), size_(std::char_traits::length(s)) {}