Set location for all non apple unixes, not just debian.

Currently, CMake on Arch configures /etc/openmw/openmw.cfg to be
```bash
data="?global?data"
data="?mw?Data Files"
data-local="?local?data"
resources=resources
```

This pull changes the resources line to `resources=/usr/share/games/openmw/resources`, something that had to be done with sed in the Arch packaging script.