it's great that we're now shipping gpg-error.pc for use on systems that have pkg-config available. Maybe we should also ship a comparable gpgrt.pc, for those who decide to use the library under its new name?
Let's wait with this until we ship a libgpgrt. I am not sure what the best way to migrate to another library name. By current idea is start with some release installing two libraries using the two names but with identical code. Some releases later we could require a configure option to install libgpg-error in addition to libgpgrt.
Are you okay with changing this issue's title to "Migrate from libgpg-error to libgpgrt" ?