I know this question was asked a lot of times, since I searched for hours for a solution, but it was never answered (or at least not for my situation).
I am using Wi
Alright, to not have to add any additional libraries (that are not needed by the server) here's what I had to do in addition to adding the Wildfly runtime library to the project: Go to Project/Properties/Project Facets/Java Server Faces and chose Library Provided by Target Runtime in the library type (instead of a User Library).