Primarily since we appear to compile require with C and not C++

This reverts commit 9b59288d.

Update CONFIG_SHELL

See merge request e3/e3-require!84

E3-752: Fetch dependencies recursively

See merge request e3/e3-require!83

* One test to catch invalid dependencies
* One test to catch architecture-dependent dependencies. Note that this itself does depend on
  the underlying architecture, which probably should be improved. But at the moment we only
  build for linux-based architectures, so this should be ok.

This uses some general make tools, most notably "while" and "select" which come from
https://github.com/markpiffer/gmtt.git and which allow us to recursively parse the
.dep files in the given e3 installation. Broadly speaking, we start with all variables
of the form `%_DEP_VERSION` to determine the first line of dependent modules, and then
we ask them (using `fetch_deps`) what they depend on.

E3-768: Fix tag fetching issue of e3 modules

See merge request e3/e3-require!81