Riccardo Tisci said his spring Givenchy collection was based in part on Tyrolian dress, which explains the dirndls. At the same time, he never strays far from an off-duty sexy nun quality, gladiator elements, or, increasingly, a plunging-V, second-skin vibe typical of Kim Kardashian — his de facto new muse, for better or worse. Here are the best looks…