Provide Makefiles in generated standalone

[phmarti]

For sharing with external parties, providing the Makefiles and build structure would be a better solution to avoid all the machinery behind the configure/build_command structure. This solution comes with a couple of problems:

1. How to generate the Makefiles for Kesch and Daint? configure relies on hostname to identify host.
2. There is no problem in storing the Makefile and build structure in the repository, but the external libraries in 'externals' are heavy and duplicated/processed in build/externals.