[release-branch.go1.17] cmd/compile: avoid adding LECall to the entry block when has opendefers

The openDeferRecord always insert vardef/varlive pairs into the entry block, it may destroy the mem chain when LECall's args are writing into the same block. So create a new block before that happens.

Fixes #49413

Change-Id: Ibda6c4a45d960dd412a641f5e02276f663c80785
Reviewed-on: https://go-review.googlesource.com/c/go/+/361410


Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Alberto Donizetti <alb.donizetti@gmail.com>
Trust: Than McIntosh <thanm@google.com>
Reviewed-by: David Chase <drchase@google.com>
(cherry picked from commit 4f083c7d)
Reviewed-on: https://go-review.googlesource.com/c/go/+/362054


Reviewed-by: Keith Randall <khr@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>