Make sure examples are always built

When building against Qt 5 release binaries, QT_BUILD_PARTS does not include
examples. However we want to unconditionally build examples, until we become
part of the Qt 5 module set.

Change-Id: Ic51d105295797e80052e3808613fc16cec709773
Reviewed-by: Andras Becsi <andras.becsi@digia.com>
Reviewed-by: Zeno Albisser <zeno.albisser@digia.com>