Doc: add section on dynamic and statically-built Qt projects
Doc: add section on dynamic and statically-built Qt projects

It's currently not documented how to have a library that can be both
dynamically and statically linked to an application.

Change-Id: Ic9130ccb7f8b476d6d91231e4eacef2caadcf1d1
Reviewed-by: Christian Kandeler <3aa99dcdd3f0cac61fb81c2a11771c0cc2497607@qt.io>

qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qt-labs/qbs,qt-labs/qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qt-labs/qbs