Problem: currently there's no way to link against ANTLR 4 statically from Swift, which is a deal-breaker if you want to ship a single binary. See cirruslabs/tart#230 for example.

Solution: normally, the type: .dynamic should be omitted from library product specification, but changing this now might break things for Swift users. Solve this by introducing a separate Swift PM product Antlr4Static that explicitly specifies type: .static.