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.

(cherry picked from commit f2fb23f23f67db841467752c2a4c2a5cb9ebde43)

Change-Id: I6239c3f9280c50f5418947f711924be59265c4ce
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>