调整user下libs的libc目录结构 (#103)

* 调整user下libs的libc目录结构

* 修正.gitignore文件的问题

* 修复无法编译的问题

Co-authored-by: longjin <longjin@RinGoTek.cn>

user/apps/shell/cmd_test.c

@@ -1,8 +1,8 @@
 #include "cmd_test.h"
-#include <libc/stdio.h>
-#include <libc/stdlib.h>
-#include <libc/string.h>
-#include <libc/unistd.h>
+#include <libc/src/stdio.h>
+#include <libc/src/stdlib.h>
+#include <libc/src/string.h>
+#include <libc/src/unistd.h>
 
 int shell_pipe_test(int argc, char **argv)
 {