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/test_signal/main.c

@@ -17,11 +17,11 @@
  * 
 */
 
-#include <libc/math.h>
-#include <libc/stdio.h>
-#include <libc/stdlib.h>
-#include <libc/time.h>
-#include <libc/unistd.h>
+#include <libc/src/math.h>
+#include <libc/src/stdio.h>
+#include <libc/src/stdlib.h>
+#include <libc/src/time.h>
+#include <libc/src/unistd.h>
 
 int main()
 {