The mongo/unittest/unittest library links to mongo/options_parser/options_parser, which has recently picked up a dependency on mongo/util/net/http_client. That library, in turn, links to mongo/executor/thread_pool_task_executor, which, ultimately, links in mongo/db/service_context. As a result, all unit tests now link the service_context code and its semi-extensive transitive dependencies, whether they need it or not.
We should find a way to not make the options subsystem (or the http subsystem) force this dependency into all unit tests.