RFR: 8240903: Add test to check that jmod hashes are reproducible [v5]

[Dongbo He]

> This creates a regression test for [JDK-8240734](https://bugs.openjdk.java.net/browse/JDK-8240734). This was once blocked 
> by a time stamp issue which has been resolved by: [JDK-8276766 ](https://bugs.openjdk.java.net/browse/JDK-8276766)
> 
> We found the issue can be produced stably with at least 64 modules.
> Note that we need to add the --date jmod option to avoid the timestamp issue.
> 
> Testing:
> Added test case fails without fix for JDK-8240734, and passes otherwise.
> Tested with tier2 on linux x86.

Dongbo He has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:

 - Merge branch 'master' into 8240903
 - Delete extra blank links
 - Change shell test io java test
 - Get date by 'date +%Y-%m-%dT%H:%M:%S%:z'
 - Update Copyright
 - 8240903: Add a regression test for JDK-8240734

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7948/files
  - new: https://git.openjdk.java.net/jdk/pull/7948/files/6b185934..34b8008d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7948&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7948&range=03-04

  Stats: 3635 lines in 166 files changed: 2489 ins; 556 del; 590 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7948.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7948/head:pull/7948

PR: https://git.openjdk.java.net/jdk/pull/7948