This patch adds a missing dependency to the echo plugin for shared
builds.
Since it fixes the last remaining example, it closes the Jira ticket.
Fixes: QTBUG-112300
Pick-to: 6.5
Change-Id: Ib1da2d7d5f5d54d7224f1c65a995f3752037e5be
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>