vtm @0.9.9u: error: no viable overloaded '='

[aeiouaeiouaeiouaeiouaeiouaeiou]

On buildbots that require macports-libcxx this happens:

[ 50%] Building CXX object CMakeFiles/vtm.dir/src/vtm.cpp.o
/opt/local/bin/clang++-mp-16   -pipe -DNDEBUG -isystem/opt/local/include/libcxx/v1 -nostdinc++ -isystem/opt/local/include/LegacySupport -I/opt/local/include -stdlib=libc++ -pthread -O2 -g -DNDEBUG -arch x86_64 -mmacosx-version-min=10.11 -std=gnu++20 -MD -MT CMakeFiles/vtm.dir/src/vtm.cpp.o -MF CMakeFiles/vtm.dir/src/vtm.cpp.o.d -o CMakeFiles/vtm.dir/src/vtm.cpp.o -c /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_sysutils_vtm/vtm/work/vtm-0.9.9u/src/vtm.cpp
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_sysutils_vtm/vtm/work/vtm-0.9.9u/src/vtm.cpp:4:
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_sysutils_vtm/vtm/work/vtm-0.9.9u/src/vtm.hpp:6:
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_sysutils_vtm/vtm/work/vtm-0.9.9u/src/netxs/desktopio/application.hpp:11:
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_sysutils_vtm/vtm/work/vtm-0.9.9u/src/netxs/desktopio/controls.hpp:6:
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_sysutils_vtm/vtm/work/vtm-0.9.9u/src/netxs/desktopio/console.hpp:6:
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_sysutils_vtm/vtm/work/vtm-0.9.9u/src/netxs/desktopio/input.hpp:6:
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_sysutils_vtm/vtm/work/vtm-0.9.9u/src/netxs/desktopio/baseui.hpp:6:
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_sysutils_vtm/vtm/work/vtm-0.9.9u/src/netxs/desktopio/richtext.hpp:6:
In file included from /opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_sysutils_vtm/vtm/work/vtm-0.9.9u/src/netxs/desktopio/directvt.hpp:5:
/opt/local/var/macports/build/_opt_bblocal_var_buildworker_ports_build_ports_sysutils_vtm/vtm/work/vtm-0.9.9u/src/netxs/desktopio/logger.hpp:56:27: error: no viable overloaded '='
                    input = {};
                    ~~~~~ ^ ~~
/opt/local/include/libcxx/v1/sstream:893:25: note: candidate function not viable: cannot convert initializer list argument to 'basic_stringstream<char>'
    basic_stringstream& operator=(basic_stringstream&& __rhs);
                        ^
/opt/local/include/libcxx/v1/iosfwd:139:32: note: candidate function (the implicit copy assignment operator) not viable: cannot convert initializer list argument to 'const basic_stringstream<char>'
    class _LIBCPP_TEMPLATE_VIS basic_stringstream;
                               ^
1 error generated.