CMakeLists.txt file not found | resolution

after the instruction:
```shell
cd spconv && python setup.py bdist_wheel
``` 

if you get an error that says:

```shell
spconv/third_party/pybind11 does not contain a CMakeLists.txt file
``` 

you need to get the submodule files with this command

```shell
git submodule update --init --recursive
``` 