That was complete failure - builders are broken,
but original cl worked fine on my system.
I will need access to builders
to test this change properly.

««« original CL description
runtime: handle all windows exception

Fixes #8006.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/145150043
»»»

TBR=rsc
R=golang-codereviews
CC=golang-codereviews
https://golang.org/cl/154180043