add test_lockfree_ring_buffer2 to the Makefile
add test_lockfree_ring_buffer2 to the Makefile

marioskogias/libfiber,brianwatling/libfiber,marioskogias/libfiber,marioskogias/libfiber,brianwatling/libfiber,brianwatling/libfiber,brianwatling/libfiber,marioskogias/libfiber