test: rebuild add-ons when their sources change

The prerequisite for rebuilding was on the binding.gyp file but the
actual sources.

PR-URL: #7262
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

Makefile

@@ -143,11 +143,15 @@ ADDONS_BINDING_GYPS := \
 	$(filter-out test/addons/??_*/binding.gyp, \
 		$(wildcard test/addons/*/binding.gyp))
 
+ADDONS_BINDING_SOURCES := \
+	$(filter-out test/addons/??_*/*.cc, $(wildcard test/addons/*/*.cc)) \
+	$(filter-out test/addons/??_*/*.h, $(wildcard test/addons/*/*.h)) \
+
 # Implicitly depends on $(NODE_EXE), see the build-addons rule for rationale.
 # Depends on node-gyp package.json so that build-addons is (re)executed when
 # node-gyp is updated as part of an npm update.
 test/addons/.buildstamp: deps/npm/node_modules/node-gyp/package.json \
-	$(ADDONS_BINDING_GYPS) \
+	$(ADDONS_BINDING_GYPS) $(ADDONS_BINDING_SOURCES) \
 	deps/uv/include/*.h deps/v8/include/*.h \
 	src/node.h src/node_buffer.h src/node_object_wrap.h \
 	test/addons/.docbuildstamp