Android: Add warning that package source dir will be copied into package

When you open the "Add AndroidManifest" dialog in Qt Creator, it refers to ANDROID_PACKAGE_SOURCE_DIR. The significance to this might not be understood by the user, so they might choose to put the manifest inside an existing directory, maybe even in the project root.

This will cause androiddeployqt to copy everything in that source directory into the build directory. If you turn off shadow builds and use the project source as package source directory, then it might fail, because it will try to copy the build directory into itself.

I suggest adding a note in the dialog about this.