internal/cpu: implement CPU feature detection for openbsd/arm64
OpenBSD 7.1 onwards expose the aarch64 ISAR0 and ISAR1 registers via sysctl:
$ sysctl machdep
machdep.compatible=apple,j274
machdep.id_aa64isar0=
153421459058925856
machdep.id_aa64isar1=
1172796674562
Implement CPU feature detection for openbsd/arm64 based on this information.
Fixes #31746
Change-Id: If8a9b2b8fc557e1aaefbcb52f4d1bd9efc43856d
Reviewed-on: https://go-review.googlesource.com/c/go/+/421875
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Joel Sing <joel@sing.id.au>
Run-TryBot: Ian Lance Taylor <iant@google.com>