[bug] inference.py mkdir

[leehanchung]

In inference.py def merge(), it uses os.mkdir() to create intermediate folders, which python doesnt like.

use os.makedirs() instead.

https://github.com/modal-labs/llama-finetuning/blob/e675b16b902cef931bbf6490f960b228357d1495/inference.py#L20C1-L21C1

[thundergolfer]

Thanks @leehanchung, closed by https://github.com/modal-labs/llm-finetuning/commit/562e6a4d5a47c241d58016896ad29bfb2e46ab0b