RFR: 8238650: Allow to override buildDate with SOURCE_DATE_EPOCH

[Kevin Rushforth]

On Fri, 7 Feb 2020 19:51:07 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>>> The OCA needs to be validated and recorded.
>> 
>> https://www.oracle.com/technetwork/community/oca-486395.html#w now has
>> `Bernhard Wiedemann - OpenJDK - bmwiedemann`
>> 
>>> As for the bug, it has been transferred to the JDK project as [JDK-8238650](https://bugs.openjdk.java.net/browse/JDK-8238650).
>> 
>> Thanks, somehow I had not got an email notification for that.
>> Also worth noting that this PR only fixes one of the sources of non-determinism in openjfx. Do I have to open a separate bug for each of them?
> 
>> Do I have to open a separate bug for each of them?
> 
> Every fix (meaning each pull request) needs a unique bug ID.

As an optional override, I am OK with the concept of having a way for the build to be reproducible.

FWIW, I have scripts that will unpack the modular jar files and diff each class as well as doing the same for a src.zip, and it's pretty easy to tell if only VersionInfo (which is the class that records the time stamps) has changed.

I note that in practice, this is useful for a certain class of builds (e.g., CI or nightly test builds), but each released build is necessarily going to be different because you want a unique time stamp and build number associated with it.

I will review this (probably some time next week) and would like @johanvos to review as well.

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

PR: https://git.openjdk.java.net/jfx/pull/99