updating to latest jsoncpp causes link error

Updating to jsoncpp top of tree, I get this link error

```
/usr/bin/ld: liblangsvr.so: undefined reference to `Json::Value::operator[](std::basic_string_view >)'
collect2: error: ld returned 1 exit status
```

Start by reproducing the reported link error while updating jsoncpp to the top of tree, then inspect the langsvr link configuration and the jsoncpp library being linked. Done means liblangsvr.so links successfully with the updated jsoncpp version and no undefined reference to Json::Value::operator[].

Written by the indexing model from the issue text.