WIP: Allow include and link dependencies for header only packages
This way, a package depending on a header-only package can receive transitive dependencies. A cleaner way would be a proper interface target, but the rewrite of our cmake system would be significantly bigger.
the body of gaudi_install_headers_with_deps is the copied parts from gaudi_add_common_build.
@clemenci what we chatted about today. usage would look like this lhcb/LHCb@2db2d450