[Config] Swappable/Movable std::streambuf requirement

From: Alexander Grund (alexander.grund_at_[hidden])
Date: 2020-05-16 14:43:29

Hello,

C++11 has  `std::basic_streambuf<char>::swap` and move operators for that defined.

However there are stdlibs which don't support that. clang 5.0 on travis e.g. fails due to that.

Is there already something in Boost.Config dealing with that case which I can `requires` on to skip the build for that case?
Most of the checks I've seen in Boost.Config are using the C++ feature test macros but for this there is none.

If it doesn't exist: Would this be something to be added to Boost.Config? Or my local build files?
How would such a test work? Can anyone point me to a similar example? I'm having trouble navigating over the many partially auto-generated files in Boost.Config.

Thanks,
Alex