RFR: 8288396: Always create reproducible builds

[Magnus Ihse Bursie]

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.

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Commit messages:
 - 8288396: Always create reproducible builds

Changes: https://git.openjdk.org/jdk/pull/9152/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=9152&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8288396
  Stats: 94 lines in 15 files changed: 11 ins; 63 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/9152.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9152/head:pull/9152

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