[tex-k] bibtex: Not writing to .build/main.blg (openout_any = p).

[Tohiko Looka]

I updated today to TeX live 2020 and I am noticing an issue that I
don't think I had before on TeX Live 2017.

I am trying to compile my tex file into a hidden sub directory using the command

pdflatex --output-directory=.build main.tex

and

bibtex .build/main

The first command runs successfully, but bibtex complains that "Not
writing to .build/main.blg (openout_any = p)."
I understand that this comes from TeX’s protection against writing to
directories that aren’t descendents of the current directory. However,
`.build` is a descendant of the current directory. Also, if I change
the name of the directory to something that does not start with . like
`build`, both commands run successfully.

Is this intentional?

-- Tohiko