The package was added to portage, (591608) but it seems nobody followed up to add it as a build dependency to the facter ebuild. Cmake will fail at config stage if the cpp-hocon is not found. Reproducible: Always
dev-ruby/facter-3.4.1 includes dev-cpp/cpp-hocon in its dependencies https://gitweb.gentoo.org/repo/gentoo.git/tree/dev-ruby/facter/facter-3.4.1.ebuild If you have a build failure, report that here.