[CMake] Building cmake: why is openssl linked?

[Paul Smith]

Hi all.

I build CMake myself.  I've noticed that on GNU/Linux by default cmake
will be linked with openssl and require these shared libraries to be
available at runtime.

Why does cmake link with these libraries?  I can't think of a reason it
might need them.  What do I lose in functionality if I force
CMAKE_USE_OPENSSL to OFF during the build?