dev-libs/klibc-1.5.20 on amd64 hardened: QA: install QA Notice: make jobserver unavailable: make[2]: warning: jobserver unavailable: using -j1. Add `+' to parent make rule. Reproducible: Always
I fixed this in 1.5.20 but did not bump as people should not have to rebuild for this. This is fixed upstream, already.