[BUG] On Windows, liboslquery will have errors on import with invalid PATH variables

**Describe the bug**

When running `import oslquery` in Python, and you have a invalid path like `C:` in your environment variables, you will get a error.

**To Reproduce**

On Windows:
- Add `C:` to `PATH`
- Important, it needs to be `C:` and not `C:\`
- Run a Python script that imports liboslquery. The simplest way is to just run https://github.com/AcademySoftwareFoundation/OpenShadingLanguage/blob/main/src/liboslquery/__init__.py directly.
- Notice you get a error message

**Evidence**

Error message:
````
Traceback (most recent call last):
File "/path/to/oslquery/__init__.py", line 10, in
os.add_dll_directory(path)
~~~~~~~~~~~~~~~~~~~~^^^^^^
File "", line 1165, in add_dll_directory
OSError: [WinError 87] The parameter is incorrect: 'C:'
```

Start with src/liboslquery/__init__.py and reproduce the import on Windows with C: included in PATH. Verify the handling of that PATH entry and confirm that importing liboslquery succeeds without the WinError 87 exception.

Written by the indexing model from the issue text.