use -- for jsc

tools/jsrun.py

@@ -15,7 +15,7 @@ def timeout_run(proc, timeout, note='unnamed process', full_output=False):
 def run_js(filename, engine=None, args=[], check_timeout=False, stdout=PIPE, stderr=None, cwd=None, full_output=False):
   if type(engine) is not list:
     engine = [engine]
-  command = engine + [filename] + (['--'] if 'd8' in engine[0] else []) + args
+  command = engine + [filename] + (['--'] if 'd8' in engine[0] or 'jsc' in engine[0] else []) + args
   return timeout_run(
     Popen(
       command,