Emerging the stable version of x11-libs/cairo-1.14.12 pulls in sys-libs/binutils-libs-2.31.1 which is keyworded. A stable package should never required a keyworded package otherwise either the stable package should be keyworded or the keyworded package should be stable.
It does not. This must be a local configuration problem. Are you using binpkgs?
Nope, I do not. Emerge shows that cairo pulls it in. Can it be an amd64 problem?