Какова наилучшая практика для ссылки на сторонние компоненты C ++ (например, библиотеки), используяrelative пути в Eclipse-CDT?

I'm trying to reference Boost and Google protobuf. I've put them each in a folder in my workspace, e.g. /home/user/workspace/boost_1_39_9 I've added a reference to that folder under build settings in the project properties, BUT eclipse won't let me specify that path as relative to the workspace folder, I have to choose it using filesystem and specify an absolute path

Спасибо,

Alex