Enable Buidling with C++17

[simonspa]

...for @LoQue90 :smile_cat:

#include <variant>

std::variant<double, int> test;
test = 3.14;

if(std::holds_alternative<int>(test)) {
   LOG(DEBUG, "Look, an int!");
} else if (std::holds_alternative<double>(test)) {
   LOG(DEBUG, "Ooooh, a tiny double!");
}