Doing a `make -jN check` from a fresh build breaks (and has probably been
broken for a while). linux_client_unittest_shlib is missing $(TEST_LIBS)
from its _DEPENDENCIES. The automake manual says if _DEPENDENCIES are not
specified they'll be computed from _LDADD, but we are specifying it and just
leaving out $(TEST_LIBS).

R=vapier@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1870733005 .