Revert "[CMake] Do not add dunegrid in UG/ALUGrid/ALBERTA flags."

Thanks to Markus for insisting that it was correct. The libs are
needed for shared linking. Due to other problems related with
-fPic it is currently only working out of the box with
Alberta.

This reverts commit 21da22d1eea248dc41bf333510324b42ee3db026.