nested flexible array member is a GCCism

This is NG. The ISO C section 6.7.2.1 explicitly states that
structs having flexible array members "shall not be a member
of a structure or an element of an array."

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61875 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

node.c

@@ -1042,7 +1042,7 @@ rb_node_init(NODE *n, enum node_type type, VALUE a0, VALUE a1, VALUE a2)
 
 typedef struct node_buffer_elem_struct {
     struct node_buffer_elem_struct *next;
-    NODE buf[FLEX_ARY_LEN];
+    NODE buf[1];
 } node_buffer_elem_t;
 
 struct node_buffer_struct {