Whenever a source file is touched that belongs to the bootstrap library,
all bootstrap tools are rebuilt. This includes moc. The moc binary
however, is a dependency whose invalidation results in a rebuilt of
quite some parts of Qt.
There's no easy way to turn off this dependency. To mitigate the
rebuilds, the bootstrap lib now can use a copy of the corelib sources.
That means the bootstrap lib is not rebuilt if its sources are changed.
This is basically the situation we had in Qt5.
The sources are not updated on reconfiguration. There's a new target
'update_bootstrap_sources' that can be built to update the copied source
tree of the bootstrap lib.
This new behavior can be controlled with the variable
QT_USE_BOOTSTRAP_SOURCE_COPY. It's on by default for developer builds.
Fixes: QTBUG-92269
Change-Id: I50234df66590c39594d208424394c7a600dc5606
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
743bb66744