cmd/compile: new escape analysis broke s390x

[mdempsky]

The s390x builder is unhappy since I enabled newescape by default; e.g.

https://build.golang.org/log/17d8a268ff942ee3fa4fa27ea8685aaa4347b689
https://build.golang.org/log/0e2023e3028d604edf2875a48664849fd1b0b53d

I'm expecting there's a s390x-specific runtime issue (like js/wasm's https://go-review.googlesource.com/c/go/+/170323/).

I don't have access to an s390x machine at the moment, so trying to debug via looking at -m output from cross-compiling for GOARCH=s390x.

/cc @mundaym for FYI

[mdempsky]

Looks like it's the same issue: https://github.com/golang/go/blob/master/src/runtime/internal/atomic/atomic_s390x.go#L49

[gopherbot]

Change https://golang.org/cl/172417 mentions this issue: runtime/internal/atomic: fix s390x's StorepNoWB implementation