Small fixes to the packaging script

* Add a .tag file to the archive that contains the sha1 the package was created from. This is useful for diagnostics.
* Use bash and enforce error handling (it's easy to accidentally include bashisms)

Change-Id: I217942da2e985772567da91a7635e5e81533ca95
Reviewed-by: Zeno Albisser <zeno.albisser@digia.com>
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>
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: I4ffb4a7d9d8e8e0a1d681dfb9d337b8ab9f76d9a
Reviewed-by: Pierre Rossi <pierre.rossi@gmail.com>
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>