Change dcd2f829 introduced fake files with the extension .cbt for custom
build tools that generate code from C++ source inputs. The moc_predefs.h
header file falls into this category, because it is generated from
dummy.cpp.
It turns out that these fake files have to exist. Otherwise the
custom build step is executed on every build. That means re-moccing all
mocables on every build.
Fix this by actually creating the fake .cbt files with some
explanatory comment in them.
Task-number: QTBUG-57695
Change-Id: I251294334425d9914677787d8ba6da1169b4cca5
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
5fc2337d74