E.g., here's the new "go build" output:
$ go build misc/cgo/errors/issue8442.go
# command-line-arguments
could not determine kind of name for C.issue8442foo
gcc errors for preamble:
misc/cgo/errors/issue8442.go:11:19: error: unknown type name 'UNDEF'
Fixes#8442.
LGTM=iant
R=iant, alex.brainman
CC=golang-codereviews
https://golang.org/cl/129160043
