Continuation of bug 2231727.
We should define more %optflags variants in such a way that users can override the distribution default using mock --target.
To be exact, %optflags should be defined for the (sub)architectures that rpm can detect, and the new ones to add are x86_64_v2, x86_64_v3 and x86_64_v4. Builds will continue to default to vanilla x86_64.