rubinius/rubinius — pull request #1927 by voxik (2012-09-26 09:50:44+00:00)
Title: Prevent exception when --preserve-prefix is used without --prefix.

Fixes the following exception:

```
$ ./configure --default-version 19 --preserve-prefix
Checking gcc: found
Checking g++: found
Checking bison: found
./configure:227:in `join': can't convert nil into String (TypeError)
from ./configure:227:in `set_filesystem_paths'
from ./configure:1709:in `run'
from ./configure:1865:in `

'
```