GVBINDIR and ctest

I’ve noticed that environment variable GVBINDIR is used to tell ctest where to find plugins, but is not documented anywhere. I found a forum thread suggesting that this was a solution to a problem finding plugins on Mac, but it’s not documented anywhere that I can find.

Can anyone explain this variable? Might it have effects on end-users if it were set?

somewhat documented here: Command Line | Graphviz