RFR: 8256216: Enable reproducible builds in jib-profiles [v2]

[Magnus Ihse Bursie]

> The time has come to actually turn on the support for reproducible builds by default in the jib profiles.

Magnus Ihse Bursie 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 two additional commits since the last revision:

 - Only enable reproducible builds for release buils. Also explicitly set --enable-reproducible-build and not just let --with-source-date set it implicitly.
 - 8256216: Enable reproducible builds in jib-profiles

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1176/files
  - new: https://git.openjdk.java.net/jdk/pull/1176/files/ba537433..35809f3d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1176&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1176&range=00-01

  Stats: 19388 lines in 420 files changed: 12098 ins; 4830 del; 2460 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1176.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1176/head:pull/1176

PR: https://git.openjdk.java.net/jdk/pull/1176