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

[Andrew Leonard]

Add a new --source-date <TIMESTAMP> (epoch milliseconds) 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>

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Commit messages:
 - 8276766: Enable jar and jmod to produce deterministic timestamped content
 - 8276766: Enable jar and jmod to produce deterministic timestamped content

Changes: https://git.openjdk.java.net/jdk/pull/6481/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6481&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8276766
  Stats: 169 lines in 10 files changed: 141 ins; 0 del; 28 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