full support of virtualenv (simplify installation)
Idea: avoid having to set environment variables to autobuild dune-py in case of
- system wide dune installations
- running dunepy in virtualenvs Focusing on case 2: In this case we make it easy to have the user install dune modules into the virtualenv. We can check if dunepy is running in a virtualenv: for example sys.real_prefix is only set if you are inside a virtualenv and sys.prefix points to your virtualenv root directory. This can be used to augment DUNE_CONTROL_PATH and PKG_CONFIG_PATH so that a dune installed into the virtualenv is automatically detected. In case that we are not in a virtualenv we could also add $HOME/.local to these parts
In addition we could also move the default location of dune-py inside the virtual env in case DUNE_PY_DIR is not set. That makes it possible to switch dune-py directories together with the virtualenv - so one could have one virtualenv for debug and one for production etc.
Further environment variable that could be important:
- DUNE_GRID_EXPERIMENTAL_GRID_EXTENSIONS and BUILD_SHARED_LIBS should both always be true and can be set in the python script.
- CMAKE_INSTALL_PREFIX is not needed for dune-py installations
- CMAKE_CXX_COMPILER_LAUNCHER: only interesting for ccache which is not really important for Bob or Alice
- CXXFLAGS: nice would be some way of choosing this once when setting up dune-py and then also be able to change it dynamically....