RFR: Add path independence

[Athijegannathan Sundararajan]

On Wed, 31 Aug 2022 07:15:33 GMT, Per Minborg <duke at openjdk.org> wrote:

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

Note: "As long as the library remains compatible.." That is not true for all samples. For eg. libffmpeg has broken compatibility. Only specific older version works.  May be the PR title should "Add path independence for libzstd sample".

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