Bug in luatex handling of hidden dirs in TEXMFVAR

[Karl Berry]

Hi Ben,

    I expect setting it to a filename beginning with a dot
    to be fairly common

True. As you noted, the default in TL for TEXMFVAR and TEXMFSYS has
always been $HOME/.texliveYYYY.
    
    I do wonder whether it would be easy to improve the error message here
    to reference the documentation.

Good thought. I'll take a look. (Or if someone wants to send a patch, so
much the better.) --thanks, karl.