[Dune] CMake: compile dune-common now fails

[Agnese, Marco]

Hi Dominic,

> You might be better off switching to out of source builds.

I am little confused. 
By default CMake use out-of-source build. Am I right?
In my case it builds inside dune-common/build-cmake. 
For my understanding this is an out-of-source build. 
Or do I need to build in build/dune-common where build/ is on the same level of dune-common?

Thank you,
cheers,
Marco