Don't set library paths if !QT_CONFIG(library)

Change-Id: Ibea22f6897ecd54a3aee1aafef6f73df03cf689f
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Yoann Lopes <yoann.lopes@qt.io>

tests/auto/unit/qmediaserviceprovider/tst_qmediaserviceprovider.cpp

@@ -83,7 +83,9 @@ private:
 void tst_QMediaServiceProvider::initTestCase()
 {
 //    QMediaPluginLoader::setStaticPlugins(QLatin1String("mediaservice"), plugins);
+#if QT_CONFIG(library)
     QCoreApplication::setLibraryPaths(QStringList() << QCoreApplication::applicationDirPath());
+#endif
 }
 
 void tst_QMediaServiceProvider::testDefaultProviderAvailable()