[libc][time]修复MDK编译环境下difftime()函数多重定义的问题 (#8174)

components/libc/compilers/common/ctime.c

@@ -325,12 +325,12 @@ char *ctime(const time_t *tim_p)
 }
 RTM_EXPORT(ctime);
 
-#ifndef __ICCARM__
+#if (!defined __ARMCC_VERSION) && (!defined __CC_ARM) && (!defined __ICCARM__)
 double difftime(time_t time1, time_t time2)
 {
     return (double)(time1 - time2);
 }
-#endif /* __ICCARM__ */
+#endif
 RTM_EXPORT(difftime);
 
 RTM_EXPORT(strftime); /* inherent in the toolchain */