message: Introduce Util::stable_keep_if()
diff: @@ -37,6 +37,12 @@ namespace vcpkg::Util
  return ret;
  }
  + template<class Container, class Pred>
  + void stable_keep_if(Container& cont, Pred pred)
  + {
  + cont.erase(std::stable_partition(cont.begin(), cont.end(), pred), cont.end());
  + }
  +
  template<class Container, class Pred>
  void unstable_keep_if(Container& cont, Pred pred)
  {
  