tools: fix node args passing in test runner

This fixes a regression from 53c88fa so that special arguments
can once again be passed to the node executable when running tests.

PR-URL: #13384
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>

tools/test.py

@@ -817,6 +817,10 @@ def GetConfiguration(self, context):
       (file, pathname, description) = imp.find_module('testcfg', [ self.path ])
       module = imp.load_module('testcfg', file, pathname, description)
       self.config = module.GetConfiguration(context, self.path)
+      if hasattr(self.config, 'additional_flags'):
+        self.config.additional_flags += context.node_args
+      else:
+        self.config.additional_flags = context.node_args
     finally:
       if file:
         file.close()