RFR: 8356657: Use stable source-date for cmp-baseline jib profiles

[Mikael Vidstedt]

The cmp-baseline builds expect the source-date to be stable across the two builds (really: invocations of configure). For CI builds the source-date gets set based on information from the job, but for local builds it gets the default "current" value which will not be the same for the two builds.

While it's possible to override this on the command line it would be more user friendly to have jib provide a stable source-date instead.

Testing: tier1,builds-tier[2-5]

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Commit messages:
 - 8356657: Use stable source-date for cmp-baseline jib profiles

Changes: https://git.openjdk.org/jdk/pull/25160/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25160&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8356657
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/25160.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25160/head:pull/25160

PR: https://git.openjdk.org/jdk/pull/25160