cmake broken when TBB is not found.
When TBB is disabled by
then the cmake process in dune-common fails with
CMake Error at dune/common/CMakeLists.txt:31 (add_dune_tbb_flags): Unknown CMake command "add_dune_tbb_flags".
Guarding the function call with
if(TBB_FOUND) add_dune_tbb_flags(dunecommon) endif()
fixes the problem. However, it may be desirable to have this if inside the function 'add_dune_tbb_flags'. It did not seem straight forward to fix this.