[lworld] RFR: 8351550: [lworld] Some bootstrap methods/lambda factories fail with -XX:+UseNullableValueFlattening

[Frederic Parain]

Fix handling of offsets for boxing classes.
Thanks to Chen Liang and John Rose for their help identifying the root cause of the problem.

Fred

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Commit messages:
 - Fix handling of offsets for boxing classes

Changes: https://git.openjdk.org/valhalla/pull/1396/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1396&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351550
  Stats: 62 lines in 2 files changed: 11 ins; 10 del; 41 mod
  Patch: https://git.openjdk.org/valhalla/pull/1396.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1396/head:pull/1396

PR: https://git.openjdk.org/valhalla/pull/1396