Spurious qmake errors in Issues pane cause unexpected dialog popup

When trying to run (with "build before run") Creator in Creator with qmake I get two errors in the issue pane

Project ERROR: process_ctrlc_stub is Windows only
Project ERROR: unknown module(s) in Qt: serialport

and afterwards a message box

Found some build errors in current task.  Do you want to ignore them?

This is on Linux, so the process_ctrlc_stub message is not "real", probably only triggered by a cumulative qmake run.