RFR: 8288396: Always create reproducible builds

[Magnus Ihse Bursie]

On Tue, 14 Jun 2022 09:48:25 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

> When we started introducing some possibly more intrusive compiler flags and functionality for reproducible builds, we also introduced a flag to turn this off  out of an abundance of caution. But we have been been using this configuration for a year or so internally within Oracle, with no issues. So there's really no reason to be able to turn this off. (If you were to ask me, the fact that compilers and build tools ever started to produce non-deterministic output has been a bug from day one.)
> 
> With this fix, all randomness should be gone from our builds, at least on linux and windows. There are no more `__DATE__` and `__TIME__` macros in the source code.

This PR also include a more "radical" version of JDK-8287894, which probably should have been adopted by JDK-8287894 in the first place. There is no need to include the build date in the assert strings for shmem on Windows.

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PR: https://git.openjdk.org/jdk/pull/9152