Those versions are broken, and sporadically reset the PKRU register on
context switches (observed on ChromeOS only). This was fixed by this
patch:
https://lore.kernel.org/all/20210623121456.399107624@linutronix.de/

Thus we detect the running kernel version (once per process), and
disable PKU if we detect a potentially broken kernel version.

R=jkummerow@chromium.org

Bug: v8:11974
Change-Id: Ib5158b4cf51d5c2811678b1b7dcc1494bc0ff46a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3417440Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78857}