Lots of errors like:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/usr/include/c++/v1/string:821:42: error: implicit instantiation of undefined template 'std::char_traits'
821 | static_assert(is_same<_CharT, typename traits_type::char_type>::value,
| ^
/opt/sw/src/fink.build/doxygen-1.9.8-1/doxygen-1.9.8/src/qcstring.h:109:21: note: in instantiation of template class 'std::basic_string' requested here
109 | m_rep.resize(s.size());
| ^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/usr/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
| ^

Google sent me to a stackoverflow link that said, "Apple officially removed support for std::char_traits in Xcode 16.3."