RFR: 8282567: Improve source-date handling in build system [v4]

[Severin Gehwolf]

On Fri, 4 Mar 2022 23:43:12 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

> As for RPM builds (by whom?)

We, Red Hat, build OpenJDK in Fedora and RHEL via `rpmbuild` :)

> suddenly being build with --enable-reproducible-build, I would not think it is a matter of concern. For linux, the only real difference --enable-reproducible-build does is add the --date flag to jmod (and to the bootjdk jar, if it supports it), and runs a special tool on src.zip to make it reproducible. The only real reason this flag exists (and not just is the default behavior) is out of an abundance of caution. On Windows, it triggers the `-experimental:deterministic` flag, which has the scary sounding word "experimental" in it. But we have been running with this option enabled for all Oracle Windows builds for years by now, I think, without seeing any problems.
> 

Fair enough.

> So I'm actually contemplating removing the --enable-reproducible-build flag, and just make that behavior default. There's very little reason not to have this turned on always, and many good reasons for having it.

+1. It would be more explicit than by sneaking this change in by starting to respect `SOURCE_DATE_EPOCH` (which it didn't before - at least consistently)

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PR: https://git.openjdk.java.net/jdk/pull/7660