Make CBL iOS Framework target support tvOS
Make CBL iOS Framework target support tvOS

This is the same fix made into release/1.2.1 branch.

amco/couchbase-lite-ios,amco/couchbase-lite-ios,amco/couchbase-lite-ios,brendand/couchbase-lite-ios,brendand/couchbase-lite-ios,amco/couchbase-lite-ios,brendand/couchbase-lite-ios,couchbase/couchbase-lite-ios,amco/couchbase-lite-ios,brendand/couchbase-lite-ios,couchbase/couchbase-lite-ios,amco/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,brendand/couchbase-lite-ios,couchbase/couchbase-lite-ios,amco/couchbase-lite-ios