Folders denoted as `append_only_caches` not accessible in `output_digest`

[ndellosa95]

Describe the bug If you set output_directories=(".",) then the folder will just not be present. If you actually try and grab a file from within the directory in question, you will see the following error:

native_engine.IntrinsicError: Snapshots must be constructed from unique path stats; got duplicates in [Some(".cache/pex_root"), Some(".python-build-standalone"), Some("target")]

Pants version 2.22.0dev3

OS WSL

Additional info As part of the pants dbt backend I'm working, I want to cache the target directory as dbt uses it as a cache but I also need to parse the content of the manifest.json file from within that target directory.

[ndellosa95]

This probably isn't so much a bug as expected behavior given what I see here but it would be nice if this was handled automatically by the engine.