RFR: 8276766: Enable jar and jmod to produce deterministic timestamped content [v14]

[Andrew Leonard]

> Add a new --source-date <TIMESTAMP> (epoch seconds) option to jar and jmod to allow specification of time to use for created/updated jar/jmod entries. This then allows the ability to make the content deterministic.
> 
> Signed-off-by: Andrew Leonard <anleonar at redhat.com>

Andrew Leonard has updated the pull request incrementally with one additional commit since the last revision:

  Update src/jdk.jlink/share/classes/jdk/tools/jmod/JmodOutputStream.java
  
  Co-authored-by: Magnus Ihse Bursie <mag at icus.se>

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6481/files
  - new: https://git.openjdk.java.net/jdk/pull/6481/files/c84bc5ad..2f3a7fc2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6481&range=13
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6481&range=12-13

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6481.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6481/head:pull/6481

PR: https://git.openjdk.java.net/jdk/pull/6481