package/libss7: new package

The Makefile in the package is not very versatile, so we need to go our
way to only build and install what we can.

Fixing the Makefile is not worth it, considering that we can quite
easily do all of that in our .mk.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
[Arnout: Add license file hash, use SPDX license name]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
4 files changed