newlib fopen "rb" mode pass the wrong arg 'flags" to _open_r with value 65536

[rqbh]

when call the fopen with mode "rb", _open_r get the wrong arg 'flags' with value 65536, replaced by "r+" , _open_r get the right args.

[mysterywolf]

Thank you for your report, and we also received a same problem from community.

更新：又有社区小伙伴报告：fopen 参数如果是rb+,会有问题。看起来只要含着b就会出问题

[mysterywolf]

Thanks for your report, we are going to fix this problem at #5267. It will be merged in recent days. Thank you!