Fix a printf format warning.

warning: format '%lu' expects argument of type 'long unsigned int', but
   argument 3 has type 'unsigned int' [-Wformat] sizeof(RangeSet) + num * sizeof(int));

Change-Id: I4a3c6fc8d40c08ea84f8f5ee13f39350e4264027

updater/blockimg.c

@@ -61,7 +61,7 @@ static RangeSet* parse_range(char* text) {
 
     RangeSet* out = malloc(sizeof(RangeSet) + num * sizeof(int));
     if (out == NULL) {
-        fprintf(stderr, "failed to allocate range of %lu bytes\n",
+        fprintf(stderr, "failed to allocate range of %zu bytes\n",
                 sizeof(RangeSet) + num * sizeof(int));
         exit(1);
     }