[potential bug] `dataset_upload` fails with symlinks

[cakiki]

I'm not sure whether this is by design, but I was trying to upload a dataset where the local directory contained symlinks to data in another local directory using kagglehub.dataset_upload and that failed so I figured I'd report it.

I'm guessing this also affects other kinds of uploads.

The data looked like this:

lrwxrwxrwx 1 akiki users  79 May  9 15:31 train-00000-of-00017.parquet -> ../../../blobs/29470164b8e5904952d0cf25375a8a813a714bebfe4238284a15af121725129b
lrwxrwxrwx 1 akiki users  79 May  9 15:31 train-00001-of-00017.parquet -> ../../../blobs/4132acf3390605b43f21d93fee349617396b5575aef6c13a3a1889a383ba2e28
lrwxrwxrwx 1 akiki users  79 May  9 15:31 train-00002-of-00017.parquet -> ../../../blobs/4ad3c7e8d538cb3b75c972debc9d1dc4501880928528b4591a43e25ced51cef1