init: Add wait command and mount wait flag

Change-Id: I6b4c10f8f246095a7fb7342388ec4f6ff97d5733
diff --git a/init/util.h b/init/util.h
index 3dadfb9..bf7928d 100644
--- a/init/util.h
+++ b/init/util.h
@@ -28,4 +28,5 @@
 void sanitize(char *p);
 void make_link(const char *oldpath, const char *newpath);
 void remove_link(const char *oldpath, const char *newpath);
+int wait_for_file(const char *filename, int timeout);
 #endif