Fix posixtest_browser suite to run again. (#25294)

Author: juj

test/test_posixtest.py

@@ -170,7 +170,7 @@ def f(self):
             '-sTOTAL_MEMORY=256mb',
             '-sPTHREAD_POOL_SIZE=40']
     if browser:
-      self.btest_exit(testfile, args=args)
+      self.btest_exit(testfile, cflags=args)
     else:
       self.do_runf(testfile, cflags=args, output_basename=name)