[LLVMdev] [RFC] Raise minimum required CMake version to 3.0

[Robinson, Paul]

> > You're still thinking about development environments, not production
> > machines (ie. buildbots). One off installations are simple in any
> > system, management of production environments are a constant source of
> > pain, Windows, OSX or Linux.
> 
> Maybe. But the point is still that we seem to be OK with putting more
> pain on Windows and OS X users (of whatever type) than Linux.

There is zero *incremental* pain to Windows for specifying a newer
version of CMake.  There is nonzero incremental pain to Linux.
--paulr