Switch back to using BOOST_TEST_DYN_LINK
Switch back to using BOOST_TEST_DYN_LINK

I'm adding BOOST_TEST_DYN_LINK back to the BoostBuild2 generator so all
unit test targets will work correctly if compiled statically.

TimSimpson/Macaroni,bowlofstew/Macaroni,TimSimpson/Macaroni,bowlofstew/Macaroni,bowlofstew/Macaroni,bowlofstew/Macaroni,TimSimpson/Macaroni,bowlofstew/Macaroni,TimSimpson/Macaroni,TimSimpson/Macaroni