CMake/Help/release/dev/drop-HP-UX.rst

drop-HP-UX
----------

* Support for building CMake on HP-UX has been dropped pending better
  support for C++11 and a port of libuv.  See `CMake Issue 17137`_.
  Use CMake 3.9 or lower instead for HP-UX support.

.. _`CMake Issue 17137`: https://gitlab.kitware.com/cmake/cmake/issues/17137