2.x: safeguard against building with v1 tags (#5219)
2.x: safeguard against building with v1 tags (#5219)


akarnokd/RxJava,artem-zinnatullin/RxJava,AttwellBrian/RxJava,AttwellBrian/RxJava,ReactiveX/RxJava,reactivex/rxjava,ReactiveX/RxJava,reactivex/rxjava,artem-zinnatullin/RxJava,NiteshKant/RxJava,NiteshKant/RxJava,akarnokd/RxJava