Relative file paths resolve incorrectly when using pyxel watch
When using pyxel watch relative paths resolved with `abspath` are incorrect.  When I run my game with:

```py
poetry run pyxel watch game ./game/main.py
```

Attempting to use `abspath` or `realpath` to resolve a path return invalid paths for any relative paths.  I use `abspath` to load resources relative to the main module, but I am unable to resolve the main modules location using  `__file__`  or using the inspect module because they return a relative path ` ./game/main.py`, and resolving path path with `abspath` gives an invalid path.  I get a path with an extra directory: `~/my/correct/path/game/game/main.py`. I am not an expert, but it looks like this is a quirk of `multiprocessing.Process`.

I was able to fix this issue in pyxel by resolving the watch module path to an absolute path in pyxel `cli.py` before sending it to `multiprocessing.Process`:

```py [pyxel/python/pyxel/cli.py]
def watch_and_run_python_script(watch_dir, python_script_file):
    python_script_file = _complete_extension(python_script_file, "watch", ".py")
    _check_dir_exists(watch_dir)
    _check_file_exists(python_script_file)
    _check_file_under_dir(python_script_file, watch_dir)
    python_script_file = os.path.abspath(python_script_file) # <= FIX HERE
    # ...
``` 

After applying this fix when resolving the `__file__` module (or any relative path) it is resolved correctly without the duplicate folder: 

```
~/my/correct/path/game/main.py  # Correct after the fix
~/my/correct/path/game/game/main.py  # Incorrect before the fix
```

I haven't testing this much to see if it creates any unintented problems but it fixed the issue for me. I'm not sure if this is an issue for other people or just myself, but I hope that this information is helpful. Also, I am on linux, I haven't tried on windows or mac.  Thank you again for creating pyxel!