cmd/compile: propagate len([]T{}) to make builtin to allow stack allocation
Updates #75620
Change-Id: I6a6a6964af4512e30eb4806e1dc7b0fd0835744f
Reviewed-on: https://go-review.googlesource.com/c/go/+/707255 Reviewed-by: Keith Randall <khr@google.com> Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Keith Randall <khr@golang.org> Reviewed-by: Carlos Amedee <carlos@golang.org>