nimble must tell us more information
```
% nimble --verbose build
Prompt: foo not found in any local packages.json, check internet for updated packages? [y/N]
    Answer: y
Downloading Official package list
     Trying https://github.com/nim-lang/packages/raw/master/packages.json
    Success Package list downloaded.
    Reading official package list
```
Minimally, I want to know the NIMBLE_DIR that's it's actually using, so I know I have provided that correctly.