Add CMake `install` and `export` commands to allow for `cmake --install`

[eyalroz]

We currently only allow for the building of artifacts in this repository, not for their installation. We should add the relevant CMake commands to indicate what should be installed and where.

This should obviate actions such as the copying of dists.dss into the build directory, effected in @adrianlut 's commit a2b21d0.