[Libc][dlib] Add STDIN_FILENO, STDOUT_FILENO and STDERR_FILENO to dlib sys/unistd.h .
#define _SYS_UNISTD_H
#ifdef RT_USING_DFS
+
+#define STDIN_FILENO 0 /* standard input file descriptor */
+#define STDOUT_FILENO 1 /* standard output file descriptor */
+#define STDERR_FILENO 2 /* standard error file descriptor */
+
#include <dfs_posix.h>
#else
#define _FREAD 0x0001 /* read enabled */
