internal/buildcfg: fix test for GOAMD64=v3 ./all.bash
If GOAMD64 is set to a bogus value, goamd64() will return the default
value, which may not necessarily be 1. Instead, just test that it sets
Error.
Change-Id: Ibbc26608c1ae24e645c7753ef5765b9c2fdc089e
Reviewed-on: https://go-review.googlesource.com/c/go/+/351129
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>