Is it possible to overwrite 'PREFIX_DIR'?

### Comment:

Hi @xhochy, greetings. First of all thanks for shipping this package on 'conda-forge' I've been using it for a long time now and it's great how easier it is to incorporate it in various scenarios. That's said, I would like to know if there is a way we can make the `PREFIX_DIR` variable present in the `build.sh` file something overridable during installation? (or change that to something we can pass)