5.15 doesn't compile: squawking about numeric_limits

$ ../qt5/configure -developer-build -debug -no-optimize-debug -confirm-license -opensource -no-tslib -no-pch -nomake tests -nomake examples
...
In file included from /home/rutledge/dev/qt5/qtbase/src/corelib/text/qbytearraymatcher.cpp:40:
/home/rutledge/dev/qt5/qtbase/src/corelib/text/qbytearraymatcher.h: In static member function ‘static QStaticByteArrayMatcherBase::Skiptable QStaticByteArrayMatcherBase::generate(const char*, uint)’:
/home/rutledge/dev/qt5/qtbase/src/corelib/text/qbytearraymatcher.h:103:38: error: ‘numeric_limits’ is not a member of ‘std’
  103 |         const auto uchar_max = (std::numeric_limits<uchar>::max)();
      |                                      ^~~~~~~~~~~~~~
...
<much more of the same, in various files>