[klibc] add RT_USING_LIBC for kstdio

Author: mysterywolf

include/klibc/kstdio.h

@@ -15,11 +15,15 @@
 extern "C" {
 #endif
 
+#ifdef RT_USING_LIBC
+
 int rt_vsprintf(char *dest, const char *format, va_list arg_ptr);
 int rt_vsnprintf(char *buf, rt_size_t size, const char *fmt, va_list args);
 int rt_sprintf(char *buf, const char *format, ...);
 int rt_snprintf(char *buf, rt_size_t size, const char *format, ...);
 
+#endif /* RT_USING_LIBC */
+
 #ifdef __cplusplus
 }
 #endif

src/klibc/kstdio.c

@@ -10,6 +10,8 @@
 
 #include <rtthread.h>
 
+#ifdef RT_USING_LIBC
+
 #define DBG_TAG           "kernel.stdio"
 #ifdef RT_DEBUG_DEVICE
 #define DBG_LVL           DBG_LOG
@@ -681,3 +683,5 @@ int rt_sprintf(char *buf, const char *format, ...)
     return n;
 }
 RTM_EXPORT(rt_sprintf);
+
+#endif /* RT_USING_LIBC */