libs in $ROOT/lib now add to $(CORE_LIBS) and $(EXTRA_LIBS) and are
automatically linked by the core and codecs/plugins respectively.
Change-Id: Iff482c792a8c8142718f6a16a450c6e2f1497c9a
Core, codecs and plugins link it separately so this gets rid of SOURCES trickery.
Don't build it for hosted targets.
Change-Id: If15ef90e93cd218a4352ae8e89eea95d3122452f