A link name was given with an empty name. Erroneous code example:

```ignore (cannot-test-this-because-rustdoc-stops-compile-fail-before-codegen)
#[link(name = "")] extern {}
// error: `#[link(name = "")]` given with empty name
```

The rust compiler cannot link to an external library if you don't give it its
name. Example:

```no_run
#[link(name = "some_lib")] extern {} // ok!
```
