Migrate the installer to python

Currently the spack_setup.sh builds the toolchains, if we migrate this to a python script, we will have the following benefits:

• we might be able to run the installer in macsos
• better control over which modules are created and in which order
• install custom variants for, e.g. of openmpi for non-HPC machines
• detect the system compiler used, and modify the spack overlays accordingly