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 4e1c6ad33542a8db86278d59ee48c5fa92b7b34b.