[Dune] Building DUNE with Cmake: Linker error

[lriedel at iup.uni-heidelberg.de]

Hi Christoph,

unfortunately, adding the flags did not solve the problem.
I added

find_package(UG REQUIRED)
add_dune_ug_flags(<target>)

to the CMakeLists.txt and also tried "add_dune_all_flags(<target>)" but
still got the same error.
I am using UG 3.11.0, CMake 3.3.0, DUNE 2.3.1

Cheers,
Lukas