Fix TestApi::linkStaticAndDynamicLibs on Darwin
Fix TestApi::linkStaticAndDynamicLibs on Darwin

On Darwin no -rpath-link argument is used. Guard the section that tests
for it.

Change-Id: I16bcdb89bb928ac63a668907349c88f55c9703e9
Reviewed-by: Christian Kandeler <3aa99dcdd3f0cac61fb81c2a11771c0cc2497607@qt.io>

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