[jdk18u] RFR: 8240903: Add test to check that jmod hashes are reproducible

[Christoph Langer]

Hi all,

This pull request contains a backport of [JDK-8240903](https://bugs.openjdk.java.net/browse/JDK-8240903), commit [96952834](https://github.com/openjdk/jdk/commit/9695283458c273c2a4121f88a2a971ad4f297d5b) from the [openjdk/jdk](https://git.openjdk.java.net/jdk) repository.

The commit being backported was authored by Dongbo He on 16 Apr 2022 and was reviewed by Alan Bateman.

Thanks!

-------------

Commit messages:
 - Backport 9695283458c273c2a4121f88a2a971ad4f297d5b

Changes: https://git.openjdk.java.net/jdk18u/pull/142/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk18u&pr=142&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8240903
  Stats: 135 lines in 1 file changed: 135 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk18u/pull/142.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18u pull/142/head:pull/142

PR: https://git.openjdk.java.net/jdk18u/pull/142