Hmm, I spoke a bit too soon. I now see one side effect of Christian's change is to break the suggested code in the devguide for using a local or private version of OpenSSL on macOS at least, e.g. supplying the paths via CPPFLAGS and LDFLAGS.  If there is a pkg-config available on the path that supplies the same values, the net effect is the same but having pkg-config available wasn't a requirement previously and should not now be.  We'll probably need to fix this in a more general way than PR 5388 proposed.  I'll try to take a look at it before beta 1 freeze but, if not, it should be fixed for beta 2.