RFR: 8321371: SpinPause() not implemented for bsd_aarch64/macOS [v3]

[Fredrik Bredberg]

> The SpinPause() function only returns 0 on bsd_aarch64 (i.e. macOS)
> 
> This PR implements SpinPause() for MacOS on AArch64 and makes it possible to choose between none, nop, isb and yield by using the OnSpinWaitInst option. The same functionality is found on AArch64 based Linux platforms.
> 
> Tested successfully on macosx-aarch64 tier1-tier5.

Fredrik Bredberg has updated the pull request incrementally with one additional commit since the last revision:

  Updated after review

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16994/files
  - new: https://git.openjdk.org/jdk/pull/16994/files/addf22d0..935f586d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16994&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16994&range=01-02

  Stats: 6 lines in 1 file changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/16994.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16994/head:pull/16994

PR: https://git.openjdk.org/jdk/pull/16994