Reuse MARBLE_PLUGIN_INSTALL_PATH.
Reuse MARBLE_PLUGIN_INSTALL_PATH.

Do not handle KDE vs Qt build specially wrt plugin install path. Also
enables non-system installation for QTONLY=OFF width designer plugins.

probonopd/marble,tzapzoor/marble,David-Gil/marble-dev,tzapzoor/marble,tzapzoor/marble,probonopd/marble,utkuaydin/marble,probonopd/marble,Earthwings/marble,tucnak/marble,tucnak/marble,quannt24/marble,Earthwings/marble,utkuaydin/marble,tzapzoor/marble,tucnak/marble,Earthwings/marble,quannt24/marble,probonopd/marble,quannt24/marble,tzapzoor/marble,David-Gil/marble-dev,quannt24/marble,utkuaydin/marble,Earthwings/marble,utkuaydin/marble,tucnak/marble,David-Gil/marble-dev,David-Gil/marble-dev,Earthwings/marble,Earthwings/marble,tucnak/marble,utkuaydin/marble,utkuaydin/marble,tzapzoor/marble,David-Gil/marble-dev,quannt24/marble,tucnak/marble,quannt24/marble,probonopd/marble,quannt24/marble,tzapzoor/marble,David-Gil/marble-dev,tucnak/marble,tzapzoor/marble,probonopd/marble,probonopd/marble