dev-libs/cl is an Erlang OpenCL binding implemented as NIFs. The respective C library is compiled to ./priv/ so the "doins" in "src_install" has to include this directory.
Created attachment 676387 [details]
Hi Benedikt, are you interested in adopting dev-libs/cl via the Proxy Maintainers project? (https://wiki.gentoo.org/wiki/Project:Proxy_Maintainers)
If not I can try adopting it myself and applying your patch.