> We need to append-to rather than set CXXFLAGS, otherwise we loose -O2 &
> -pipe. Currently this results in zeromq being built without optimizations
> at all (or whatever the compiler would default too, essentially always -O0).
>
> Bdb is the same, for the CXX portion of its code. C code has been built
> with -O2.
>
> Boost has actually been uneffected because it receives -O3 from it's own
> build flags.
Also use c++17 for protofub
This is a backport of core#22840