Related Slack thread.

There are two issues:

1. The EmbraceObjCUtilsInternal module has two module map files. The existing rules_swift_package_manager code treats this as an error. The fix is to warn the client and just use the first one that is found.
2. The GRDB.swift package, a transitive dependency, defines a systemLibrary target. rules_swift_package_manager does not yet support these target types.