CN: fix the failing memcpy test

It turns out the issue was trivial and obvious.

tests/cn/get_from_arr.c

@@ -0,0 +1,20 @@
+
+/* originally made by minimising a problematic case from memcpy.c */
+
+
+char
+get_from_arr (char *in_arr)
+/*@ requires take IA = each (integer j; 0 <= j && j < 10)
+ {Owned<char>(in_arr + (j * sizeof<char>))} @*/
+/*@ ensures take IA2 = each (integer j; 0 <= j && j < 10)
+ {Owned<char>(in_arr + (j * sizeof<char>))} @*/
+{
+ char c;
+
+ /*@ extract Owned<char>, 4; @*/
+ /*@ instantiate good<char>, 4; @*/
+ c = in_arr[4];
+
+ return c;
+}
+

tests/cn/memcpy.c

@@ -24,6 +24,7 @@ naive_memcpy (char *in_arr, char *out_arr, int i)
  /*@ inv {out_arr} unchanged @*/
  {
  /*@ extract Owned<char>, j; @*/
+ /*@ instantiate good<char>, j; @*/
  out_arr[j] = in_arr[j];
  }