sandbox: add lseek helper

Follow up patches want to be able to seek fd's.

Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

include/os.h

@@ -48,6 +48,21 @@ ssize_t os_read(int fd, void *buf, size_t count);
  */
 ssize_t os_write(int fd, const void *buf, size_t count);
 
+/**
+ * Access to the OS lseek() system call
+ *
+ * \param fd	File descriptor as returned by os_open()
+ * \param offset	File offset (based on whence)
+ * \param whence	Position offset is relative to (see below)
+ * \return new file offset
+ */
+off_t os_lseek(int fd, off_t offset, int whence);
+
+/* Defines for "whence" in os_lseek() */
+#define OS_SEEK_SET	0
+#define OS_SEEK_CUR	1
+#define OS_SEEK_END	2
+
 /**
  * Access to the OS open() system call
  *