runtime: adjust comments for auxv getAuxv

runtime: adjust comments for auxv getAuxv

github.com/cilium/ebpf no longer accesses getAuxv using linkname but now
uses the golang.org/x/sys/unix.Auxv wrapper introduced in
go.dev/cl/644295.

Also adjust the list of users to include x/sys/unix.

Updates #67839
Updates #67401

Change-Id: Ieee266360b22cc0bc4be8f740e0302afd7dbd14f
Reviewed-on: https://go-review.googlesource.com/c/go/+/646535
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>