QtCore: implicit instantiation of undefined template 'std::char_traits<unsigned char>' (libc++ 19 / musl libc / amd64)

/mnt/b/yoe/master/build/tmp/work/riscv64-yoe-linux-musl/qtbase/6.7.2/image/usr/include/QtCore/qanystringview.h:135:35: error: implicit instantiation of undefined template 'std::char_traits<QChar>'
     135 |             return qsizetype(std::char_traits<Char>::length(str));
         |                                   ^
   /mnt/b/yoe/master/build/tmp/work/riscv64-yoe-linux-musl/qtbase/6.7.2/image/usr/include/QtCore/qanystringview.h:174:37: note: in instantiation of function template specialization 'QAnyStringView::lengthHelperPointer<QChar>' requested
   ↪ here
     174 |         : QAnyStringView{str, str ? lengthHelperPointer(str) : 0} {}
         |                                     ^
   /mnt/b/yoe/master/build/tmp/work/riscv64-yoe-linux-musl/qtbase/6.7.2/git/tests/auto/corelib/text/qanystringview/tst_qanystringview.cpp:685:14: note: in instantiation of function template specialization 'QAnyStringView::QAnyStringView<
   ↪ const QChar *, true>' requested here
     685 |     QCOMPARE(QAnyStringView(null).size(), qsizetype(0));
         |              ^
   /mnt/b/yoe/master/build/tmp/work/riscv64-yoe-linux-musl/qtbase/6.7.2/git/tests/auto/corelib/text/qanystringview/tst_qanystringview.cpp:344:9: note: in instantiation of function template specialization 'tst_QAnyStringView::fromLiteral<
   ↪ QChar>' requested here
     344 |         fromLiteral(str);
         |         ^