All constant expressions are non-potentially-throwing in C++14, but that is *not* the case in C++17. Change these tests of the `variant`-flavored overloads of `std::get` to expect the correct behavior when the compiler is not GCC or is GCC 9+.
Credit to Jonathan Wakely for providing an improved version of my initial change that validates the incorrect behavior on GCC < 9 as well as validating the correct behavior on other compilers.
Differential Revision: https://reviews.llvm.org/D61033
llvm-svn: 359220
413732354d