make clean failes to cleanup everything

[Tijl Coosemans]

On Tue, 4 Oct 2016 09:52:23 +0200 Gerhard Schmidt <schmidt at ze.tum.de> wrote:
> make clean fails to clean autoconf and automake.
> 
> If a port uses autoconf and autoconf isn't installed on the system, it
> will be build and installed.
> 
> if you run make clean after installing the port, every dependency is
> cleaned as well but not autoconf.

Can you give an example of such a port, because we have two mechanisms
that can pull in autoconf.