Integrated: 8282567: Improve source-date handling in build system

[Magnus Ihse Bursie]

On Wed, 2 Mar 2022 16:52:12 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

> When doing reproducible builds, controlling the build time is imperative. To make this as easy as possible, some changes are needed in the build system.
> 
>  * If source-date is set to anything other than "updated" (meaning that it should be determined at build time), then the default value of --with-hotspot-build-time should be the same time.
> 
> * If the industry standard SOURCE_DATE_EPOCH is set when running configure, the default value for --with-source-date should be picked up from this variable. (If the command line option is given, it will override the environment variable however.)
> 
> * Finally the code can be made a bit clearer that we can set and export SOURCE_DATE_EPOCH to SOURCE_DATE in spec.gmk, unless we're using the "updated" (determined at build time) value.

This pull request has now been integrated.

Changeset: 5d5bf16b
Author:    Magnus Ihse Bursie <ihse at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/5d5bf16b0af419781fd336fe33d8eab5adf8be5a
Stats:     199 lines in 8 files changed: 108 ins; 28 del; 63 mod

8282567: Improve source-date handling in build system

Reviewed-by: erikj, sgehwolf

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