misleading warning about linux/can.h not being found

I need to have host CAN tools around for a cross build (see QTBUG-106217), so I at least want to build as less of this code as possible. When I go and say:

cmake -D QT_FEATURE_socketcan=OFF ...

I will always get the warning

QtSerialBus: Cannot find linux/can.h and linux/can/raw.h Linux headers for socketCAN support.

The headers would actually be found if the tests were run, but this is the code from configure.cmake:

CONDITION LINUX AND NOT QT_FEATURE_socketcan

So whenever this feature is off the warning is shown, even if it is not the test that failed, but I requested it to be off.