make: add lnprototests to check!!

We've got great protocolo levle tests written, let's make sure we
put them to good use!

Author: niftynei

Makefile

@@ -374,7 +374,14 @@ endif
 
 check-units:
 
-check: check-units installcheck pytest
+check: check-units installcheck check-protos pytest
+
+check-protos: $(ALL_PROGRAMS)
+ifeq ($(PYTEST),)
+	@echo "py.test is required to run the protocol tests, please install using 'pip3 install -r requirements.txt', and rerun 'configure'."; false
+else
+	@(cd external/lnprototest && PYTHONPATH=$(PYTHONPATH) LIGHTNING_SRC=../.. $(PYTEST) --runner lnprototest.clightning.Runner $(PYTEST_OPTS))
+endif
 
 pytest: $(ALL_PROGRAMS)
 ifeq ($(PYTEST),)