When I did that, it copied the `bin` directory into the prefix bin and audit complains.

```
mruby:
 * Non-executables were installed to "/Users/colin/Source/homebrew/Cellar/mruby/1.0.0/bin".
The offending files are:
  /Users/colin/Source/homebrew/Cellar/mruby/1.0.0/bin/bin

Error: 1 problems in 1 formulae
```

Am I missing something?