QtAutogen: Do not re-generate AUTORCC outputs on every build
Refactoring in commit cf679ea8 removed the unconditional creation of the <target>_automoc.cpp
file. Now it is generated only when AUTOMOC
is enabled. However, if this file is not created then our internal GenerateAll
setting is enabled on every build, causing AUTORCC
to re-generate its file(s) every time. Fix the GenerateAll
setting to be used only for when autogen settings change. The old logic was left from when we had only automoc.
Closes: #16413 (closed)