internal/abi, internal/buildcfg: always enable register ABI on ARM64
In last cycle we developed register ABI for ARM64, enabled by
default as a GOEXPERIMENT. This cycle we turn it on all the time.
Later CLs will clean up fallback code.
To support in-development platforms (e.g. RISC-V), separate the
boolean variables for in-development platforms and always-on
platforms.
Change-Id: I97c27f6aeccc85ccc57eed2abd783b176da3ad80
Reviewed-on: https://go-review.googlesource.com/c/go/+/393364
Trust: Cherry Mui <cherryyz@google.com> Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>