[crac] RFR: 8373781: [CRaC] Permit -XX:CPUFeatures on other platforms [v2]

[Radim Vansa]

> Currently `-XX:CPUFeatures` option is available only on `x86_64`. This complicates creating multiarch container images that are meant to be universally runnable (with `-XX:CPUFeatures=generic`).
> 
> I propose to make this option available on all architectures, with the non-arch specific values:
> * `generic`
> * `native`
> * `ignore`
> 
> The implementation on non-x86_64 will only validate the sanity of the value.
> 
> The related option `-XX:+ShowCPUFeatures` will print an informative message (saying that the option does not make much sense).
> 
> `-XX:+IgnoreCPUFeatures` will be permitted as well, but it will be a no-op on the other architectures.

Radim Vansa has updated the pull request incrementally with two additional commits since the last revision:

 - Replace shell-based test with Java test & add other checks
 - Fix wording

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

Changes:
  - all: https://git.openjdk.org/crac/pull/282/files
  - new: https://git.openjdk.org/crac/pull/282/files/1e92e5ec..2a0aecd1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=crac&pr=282&range=01
 - incr: https://webrevs.openjdk.org/?repo=crac&pr=282&range=00-01

  Stats: 172 lines in 4 files changed: 119 ins; 49 del; 4 mod
  Patch: https://git.openjdk.org/crac/pull/282.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/282/head:pull/282

PR: https://git.openjdk.org/crac/pull/282