cmake: change test message overwrite to macro

Fixes: #79052

The yaml CMake tests overwrites `message()` in order to verify correct
error handling. This was original done in a function and then using
a return call when an expected error has been raised.
Using a function() means the `return()` only returns the `message()`
and thus wrongly continue processing rest of the yaml file.

Change `message()` to macro so the return call correctly returns from
the calling yaml functions.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>