cmd/link: sort allocated ELF section headers by address

cmd/link: sort allocated ELF section headers by address

For an executable, emit the allocated section headers in address order,
so that section headers are easier for humans to read.

Change-Id: Ib5efb4734101e4a1f6b09d0e045ed643c79c7c0a
Reviewed-on: https://go-review.googlesource.com/c/go/+/718620
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Bypass: David Chase <drchase@google.com>
Reviewed-by: David Chase <drchase@google.com>