[release-branch.go1.14] cmd/link: detect trampoline of deferreturn call

This is a backport of CL 234105. This is not a clean cherry-pick,
as CL 234105 is for the new linker, whereas we still use the old
linker here. This CL backports the logic.

The runtime needs to find the PC of the deferreturn call in a few
places. So for functions that have defer, we record the PC of
deferreturn call in its funcdata.

For very large binaries, the deferreturn call could be made
through a trampoline. The current code of finding deferreturn PC
fails in this case. This CL handles the trampoline as well.

Fixes #39991.
Updates #39049.

Change-Id: I929be54d6ae436f5294013793217dc2a35f080d4
Reviewed-on: https://go-review.googlesource.com/c/go/+/234105


Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/240917


Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Joel Sing <joel@sing.id.au>