[boost] Appveyor setup for msvc-14.1 toolset

I have added an Appveyor test to some Boost libraries, but if I specify toolset=msvc-9.0,msvc-10.0,msvc-11.0,msvc-12.0,msvc-14.0,msvc-14.1 on the b2 test script command line the run fails when it gets to 14.1, due to not finding 'cl', but succeeds for the others. What is the magical Appveyor incantation to test the latest VC++ ? I would like to avoid the environment/matrix gunk I see in other appveyor.yml files, but if it is the only way to get msvc-14.1 tests with Appveyor I will use it.