cmd/compile: keep internal/runtime packages sorted

cmd/compile: keep internal/runtime packages sorted

This is a minor cleanup from CL 600436.

For #65355.

Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest,gotip-darwin-amd64-longtest
Change-Id: I8e27f0c6ba6bd35f4aa2b9d53c394fb5f1eb433d
Reviewed-on: https://go-review.googlesource.com/c/go/+/595116
Reviewed-by: Austin Clements <austin@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>