[jdk11u-dev] RFR: 8240903: Add test to check that jmod hashes are reproducible

[Christoph Langer]

On Sun, 29 May 2022 20:43:01 GMT, Christoph Langer <clanger at openjdk.org> wrote:

> This backports a test which should have been added with [JDK-8240734](https://bugs.openjdk.java.net/browse/JDK-8240734) in first place.
> I had to do a few modifications to make it work in 11, extracted into the second commit. In 11, Files::mismatch is missing and jmod does not have the option --date.
> I verified that the test fails without the changes of [JDK-8240734](https://bugs.openjdk.java.net/browse/JDK-8240734) and passes now with it.

Windows GHA unrelated, will be fixed via https://github.com/openjdk/jdk11u/pull/39

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PR: https://git.openjdk.java.net/jdk11u-dev/pull/1115