runtime: increase freebsd/amd64 pointer size from 48 to 57 bits
Because freebsd is now enabling la57 by default.
Fixes #49405
Change-Id: I30f7bac8b8a9baa85e0c097e06072c19ad474e5a
Reviewed-on: https://go-review.googlesource.com/c/go/+/670715
Auto-Submit: Keith Randall <khr@golang.org> Reviewed-by: Keith Randall <khr@google.com> Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>