Fixing compile in Mac OS X if using luajit.

When trying to use the `luadist-git` in luajit, I end with the following error message:

```
luadist: not enough memory for state
```

This did not happen on linux, I ended up finding the solution in luajit `CMakeLists.txt` file: https://github.com/LuaDist/luajit/blob/master/CMakeLists.txt#L87.

In tests, this change did not compromise the default lua, but I believe the right would be check which lua distribution, and after this apply this patch.