Draft: Add helper script to generate super build projects
Script helper to set up super builds with pure CMake:
# get some modules
mkdir dune; cd dune
git clone https://gitlab.dune-project.org/core/dune-common.git
git clone https://gitlab.dune-project.org/core/dune-geometry.git
git clone https://gitlab.dune-project.org/core/dune-localfunctions.git
git clone https://gitlab.dune-project.org/core/dune-istl.git
git clone https://gitlab.dune-project.org/core/dune-grid.git
# generate super build project
cmake -P dune-common/cmake/scripts/GenerateDuneSuperBuild.cmake
# generate a Ninja configuration in a directory named `build`
cmake . -G Ninja -B build/
# start the actual build
cmake --build build/