TestNegativeUid tests code in cgo_lookup_unix.go, so let's use
the very same go:build line for the test file, and rename
the test file accordingly.
Change-Id: Iee3dbc25aeb8a7659c734d97dde3e9c670e80fae
Reviewed-on: https://go-review.googlesource.com/c/go/+/702976
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Mark Freeman <markfreeman@google.com> Reviewed-by: Ian Lance Taylor <iant@golang.org> Reviewed-by: Michael Knyszek <mknyszek@google.com>