Error when building example configurations with cabal

When building `yi-emacs-vty-static` with `cabal` gives the following error message:

```
cabal: Unknown target '.'.
There is no component '.'.
The project has no package directory '.'.
```

A workaround is to make a file called `cabal.project` with the following contents:

```
packages: .
```

These `cabal.project` files should probably just be added to this repository.