RFR: Layout updates

[Per Minborg]

This PR updates jextract to work with the recent changes in Panama.

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Commit messages:
 - Update to reflect recent changes in Panama

Changes: https://git.openjdk.org/jextract/pull/62/files
 Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=62&range=00
  Stats: 18 lines in 4 files changed: 14 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jextract/pull/62.diff
  Fetch: git fetch https://git.openjdk.org/jextract pull/62/head:pull/62

PR: https://git.openjdk.org/jextract/pull/62