[libc] fix compiling warning

components/dfs/src/dfs_posix.c

@@ -537,12 +537,17 @@ struct dirent *readdir(DIR *d)
     if (fd == RT_NULL)
     {
         rt_set_errno(-DFS_STATUS_EBADF);
-
         return RT_NULL;
     }
 
-    if (!d->num ||
-        (d->cur += ((struct dirent *)(d->buf + d->cur))->d_reclen) >= d->num)
+    if (d->num)
+    {
+        struct dirent* dirent_ptr;
+        dirent_ptr = (struct dirent*)&d->buf[d->cur];
+        d->cur += dirent_ptr->d_reclen;
+    }
+
+    if (!d->num || d->cur >= d->num)
     {
         /* get a new entry */
         result = dfs_file_getdents(fd,

components/libc/newlib/syscalls.c

@@ -3,6 +3,14 @@
 #include <sys/time.h>
 #include <rtthread.h>
 
+#ifdef RT_USING_DFS
+#include <dfs_posix.h>
+#endif
+
+#ifdef RT_USING_PTHREADS 
+#include <pthread.h>
+#endif
+
 /* Reentrant versions of system calls.  */
 
 int