Apparently not everybody wants to use QMake to build cppcheck. Which is
understandable if you only want to hack on/build lib and cli. Qt and QMake are
pretty lot to install for just that.
So lets start using CMake. It is widely used and is "just" build system and not
programming framework. CMake is also easy to use for building Qt software too
so it can replace QMake.
This first commit only builds lib and cli for Linux.