bsp][LPC55S69] README文档增加keil版本编译报错解决方案 (#6910)

bsp/lpc55sxx/lpc55s69_nxp_evk/README.md

@@ -87,7 +87,19 @@ On the menuconfig page, configure and select the corresponding chip model, if th
 
 **MDK and IAR must manually select the chip signal once in the project after the project is built, otherwise a serious compilation error will be generated.**
 
+---
 
+Note: Because some versions of Keil5 have issues with AC6 compiler support, it is recommended to upgrade keil to the latest version
+
+> [Download the latest version of Keil here](https://www.keil.com/update/check.asp?P=MDK&V=5.38.0.0&S=)
+
+Some error messages are as follows:
+
+![](./figures/bug.png)
+
+Or you can choose to refer to this forum post:[AC6 compiler error unsupported option '--c99' solution](https://club.rt-thread.org/ask/question/4c744e41ded5efb0.html)
+
+---
 
 5) Compile
 

bsp/lpc55sxx/lpc55s69_nxp_evk/README_zh.md

@@ -89,7 +89,17 @@ LPC55S69 是由恩智浦NXP半导体推出的基于Cortex-M33内核的高性能
 
 **MDK 与 IAR 在生成完成工程之后一定要在工程中手动选择一次芯片信号，否则会产生严重编译错误**
 
+---
 
+注意：由于Keil5有部分版本对AC6编译器支持有问题，这里建议将keil升级为最新版本
+
+> 此处附上Keil[最新版下载官网](https://www.keil.com/update/check.asp?P=MDK&V=5.38.0.0&S=)
+
+下面是部分编译报错信息：
+
+![](./figures/bug.png)
+
+或参考此论坛博文：[AC6编译报错unsupported option '--c99'解决办法](https://club.rt-thread.org/ask/question/4c744e41ded5efb0.html)
 
 5) 编译