build: more accurate dependencies on Boost libraries

See also named-data/ndn-cxx@5686c51b87b6a642aa2dc8d93e061caebbb226cc

Change-Id: I0ff9b60ae9a5e51f597d16221bbe1d97afc9704a
diff --git a/tests/wscript b/tests/wscript
index 8b3ecbe..810f726 100644
--- a/tests/wscript
+++ b/tests/wscript
@@ -1,8 +1,11 @@
+# -*- Mode: python; py-indent-offset: 4; indent-tabs-mode: nil; coding: utf-8; -*-
+
 top = '..'
 
 def build(bld):
-    bld.program(target='../unit-tests',
-                name='unit-tests',
-                source=bld.path.ant_glob('**/*.cpp'),
-                use='PSync',
-                install_path=None)
+    bld.program(
+        target=f'{top}/unit-tests',
+        name='unit-tests',
+        source=bld.path.ant_glob('**/*.cpp'),
+        use='BOOST_TESTS PSync',
+        install_path=None)