Fix package builds against release builds of Qt

The Qt build system assumes that when building a module against a release
build of Qt, syncqt was already run at package creation time. So we have to
run syncqt when creating source packages.

This patch changes the syntax to separate the file name base from the
package version to use.

Change-Id: I48897d52a917194be6662a26268ad403883ed9e0
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>