[build2] Error message for output dir missing

[Boris Kolpackov]

Moldmann Max (DC-MH/ENG52-NA) <Max.Moldmann at boschrexroth-us.com> writes:

> I noticed that build2 doesn't put out a helpful error message, when
> the output directory is not existing.

I am unable to reproduce this. Can you be more specific about what
"output directory is not existing" exactly means?

Thanks,
Boris