Hi Maxim - thanks for the report and doing the research to find that old answer. Do you have any ideas for a better solution? I can't think of one. We can't change Automake syntax now. Nor does it seem maintainble for automake to have special knowledge of all of make's builtin conditionals and match them too.
I'll see about adding something to the manual about the workaround, at least. --thanks, karl.