cmd/release: use replace windows-386-gce builder with windows-386-2008

Also, adds a test that would have failed CL 51432.

Change-Id: Icdc5b8a1a94efecd4422618b58ea4733002f0819
Reviewed-on: https://go-review.googlesource.com/53632
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/cmd/release/release.go b/cmd/release/release.go
index 5d44230..3059075 100644
--- a/cmd/release/release.go
+++ b/cmd/release/release.go
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// TODO(adg): add flag so that we can choose to run make.bash only
-
 // Command release builds a Go release.
 package main
 
@@ -198,7 +196,7 @@
 	{
 		OS:      "windows",
 		Arch:    "386",
-		Builder: "windows-386-gce",
+		Builder: "windows-386-2008",
 	},
 	{
 		OS:      "windows",