[release-branch.go1.16] cmd/link: use SHT_INIT_ARRAY for .init_array section

For #50295
Fixes #50296

Change-Id: If55ebcd5f2af724da7c9c744458a56d21a7ddde7
Reviewed-on: https://go-review.googlesource.com/c/go/+/373734


Trust: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
(cherry picked from commit cfb0cc35)
Reviewed-on: https://go-review.googlesource.com/c/go/+/374234


Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>