RFR: 8350666: cmp-baseline builds fail after JDK-8280682

[Calvin Cheung]

A fix for initializing the `_timestamp` field in `AOTClassLocation` properly so that the cmp-baseline builds are successful.

Sanity tested with builds-tier5.

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Commit messages:
 - 8350666: cmp-baseline builds fail after JDK-8280682

Changes: https://git.openjdk.org/jdk/pull/23787/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23787&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8350666
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23787.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23787/head:pull/23787

PR: https://git.openjdk.org/jdk/pull/23787