Make argument parsing strict

Author: bterlson

lib/cli.js

@@ -1,5 +1,6 @@
 const yargs = require('yargs');
 const yargv = yargs
+  .strict()
   .usage('Usage: test262-harness [options] <test-file-glob>')
   .demand('hostType')
   .describe('hostType', 'eshost host type (ch, d8, jsshell, chrome, firefox, etc.)')