Related to #607.

If the configFile option is set to a path and points to a tsconfig.json outside the respective entry point's parent directory chain, the config file will be found and used, but the webpack process will throw errors. (Usually that's a TS18003: No inputs were found in config file).

I assume this is TypeScript not being able to handle the "unusual" location of the tsconfig.json.

I'll investigate this and see what we can do about this.