Warn or handle deactivated dependencies

[saul.hazledine@…]

In the situation where a new port, A, is being installed and depends on a port B.

If B is installed (but deactivated) A will start installing and then hit an error during the build. The error appears as a build error to the untrained eye.

As a new user, I thought there was an error with the port and raised a ticket when none needed to be raised. I feel bad about this but suspect I wasn't the first person to install on a deactivated dependency and then get a build error.

There are many different behaviours that could be less confusing to people like myself. As a suggestion though, would it be possible to warn the user if a dependency was deactivated?

[vinc17@…]

Dup of #7361.