run_tests: set Node runtime variable when using default compiler
diff --git a/tools/run_tests/run_tests.py b/tools/run_tests/run_tests.py
index ab719a6..5aae343 100755
--- a/tools/run_tests/run_tests.py
+++ b/tools/run_tests/run_tests.py
@@ -377,6 +377,7 @@
                                          'node4', 'node5', 'node6',
                                          'node7', 'electron1.3'])
     if self.args.compiler == 'default':
+      self.runtime = 'node'
       self.node_version = '4'
     else:
       if self.args.compiler.startswith('electron'):