test: change buffer offset to accommodate V8 BackingStore

To avoid problem with the behavior of new V8 BackingStore API,
change the offset. The base address of each test case will be
different.

Fixes: #31061

PR-URL: #31171
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/addons/buffer-free-callback/test.js

@@ -16,20 +16,24 @@ function check(size, alignment, offset) {
   global.gc();
 }
 
+// NOTE: If adding more check() test cases,
+// be sure to not duplicate alignment/offset.
+// Refs: https://github.com/nodejs/node/issues/31061#issuecomment-568612283
+
 check(64, 1, 0);
 
 // Buffers can have weird sizes.
-check(97, 1, 0);
+check(97, 1, 1);
 
 // Buffers can be unaligned
 check(64, 8, 0);
 check(64, 16, 0);
 check(64, 8, 1);
 check(64, 16, 1);
-check(97, 8, 1);
-check(97, 16, 1);
 check(97, 8, 3);
 check(97, 16, 3);
+check(97, 8, 5);
+check(97, 16, 5);
 
 // Empty ArrayBuffer does not allocate data, worth checking
-check(0, 1, 0);
+check(0, 1, 2);