Add dependency on boost_test instead of boost_unit_test_framework lib

boost_test toolfile was added to CMSDIST, which incl.
boost_unit_test_framework. Add dependency on the toolfile instead of
attempting to link to boost_unit_test_framework directly.

https://github.com/cms-sw/cmsdist/pull/1180

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>