Makefile: fix impacts target for Cygwin environments

Author: thvnx

Makefile

@@ -43,7 +43,7 @@ doc:
 	cd lkql_checker/doc && make generate html-all
 
 impacts:
-	[ -f $(KP_JSON) ] || PYTHONPATH=$(IMPACTDB_DIR) $(PYTHON) ./utils/impact-db_impacts_gen.py $(IMPACTDB_DIR)
+	[ -f "$(KP_JSON)" ] || PYTHONPATH="$(IMPACTDB_DIR)" "$(PYTHON)" "./utils/impact-db_impacts_gen.py" "$(IMPACTDB_DIR)"
 
 format:
 	gnatformat -P lkql_checker/gnatcheck.gpr --no-subprojects