[CMake] [ANNOUNCE] cmake.org and gitlab.kitware.com downtime

[Robert Maynard]

CMake Users,

Kitware NY is moving into a new office building on Dec 15th. This
involves moving the company's network infrastructure. As a result,
there will be downtime for cmake.org, cmake.org/cmake/help/,
open.cdash.org, and gitlab.kitware.com.

We expect that these sites will be unavailable all day Dec. 15th while we
physically move everything and complete the network cutover. There
is a good chance of network connectivity being unstable for a few days
afterwards while we troubleshoot and fix any issues.