RFR: Add path independence [v2]

[Per Minborg]

> This small PR incorporated feedback from the original PR: https://github.com/openjdk/jextract/pull/66 made after it was integrated.

Per Minborg has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:

 - Merge panama and mention specific version
 - Add path independence

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Changes: https://git.openjdk.org/jextract/pull/68/files
 Webrev: https://webrevs.openjdk.org/?repo=jextract&pr=68&range=01
  Stats: 13 lines in 4 files changed: 6 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jextract/pull/68.diff
  Fetch: git fetch https://git.openjdk.org/jextract pull/68/head:pull/68

PR: https://git.openjdk.org/jextract/pull/68