runtime: revert entry point on freebsd/arm64
CL 706175 unified some arm64 entry points. However, the entry point for
freebsd/arm64 is incorrect and builds now fail. This change reverts the
freebsd/arm64 entry point and adds additional context for the future.
Fixes #76958
Change-Id: Ib9e9b7844706f7b0ef54bd449411fefc8f10bc43
GitHub-Last-Rev:
70064d8126f8ff7e2c0e5e8d4b00177c627f4d76
GitHub-Pull-Request: golang/go#76959
Reviewed-on: https://go-review.googlesource.com/c/go/+/731980
Auto-Submit: Austin Clements <austin@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>