CGAL_DATA_DIR should be set

### Solution to issue cannot be found in the documentation.

- [X] I checked the documentation.

### Issue

When compiling downstream packages, the following warning is thrown:

```
CMake Warning at /home/conda/feedstock_root/build_artifacts/colmap_1658363170573/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_plac/lib/cmake/CGAL/CGALConfig.cmake:92 (message):
CGAL_DATA_DIR cannot be deduced, set the variable CGAL_DATA_DIR to set the
default value of CGAL::data_file_path()
```

We should probably create an activate script which sets `CGAL_DATA_DIR`.

### Installed packages

```shell
cgal-cpp: 5.4.1-hbcf293a_0 conda-forge
```

### Environment info

```shell
N/A
```