runtime: mark amd64 runtime·rt0_go as NOFRAME

runtime: mark amd64 runtime·rt0_go as NOFRAME

This CL adds the NOFRAME flag to runtime·rt0_go, which should
had been added in CL 459395 but didn't and broke fix windows-amd64-2008.

Change-Id: I4583f2034bf114e1f7aaddef9ba505f53536c3eb
Reviewed-on: https://go-review.googlesource.com/c/go/+/463120
Run-TryBot: Quim Muntal <quimmuntal@gmail.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Quim Muntal <quimmuntal@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>