ext2simg: use a standard flexible array

Use a standard flexible array instead of a nonstandard zero-length
array.  No change in behavior.

Change-Id: Ifdce24f5d6e2471634bb785527def3fe8fefc202
Signed-off-by: Eric Biggers <ebiggers@google.com>
diff --git a/contrib/android/ext2simg.c b/contrib/android/ext2simg.c
index efb4e41..9b594f3 100644
--- a/contrib/android/ext2simg.c
+++ b/contrib/android/ext2simg.c
@@ -58,7 +58,7 @@
 
 static struct buf_item {
 	struct buf_item	    *next;
-	void		    *buf[0];
+	void		    *buf[];
 } *buf_list;
 
 /*