dashboard, cmd/release: use Jessie for release builds

Drop linux-amd64-stretch (which is redundant with linux-amd64, which
is now Stretch since CL 170282) and add linux-amd64-jessie, and use
Jessie in cmd/release for Linux releases)

Updates golang/go#31293

Change-Id: I21b7a43a24385d5976296d0e5f1c6009cbc18b05
Reviewed-on: https://go-review.googlesource.com/c/build/+/171121
Reviewed-by: Andrew Bonventre <[email protected]>

Author: bradfitz

cmd/release/release.go

@@ -164,7 +164,7 @@ func (b *Build) logf(format string, args ...interface{}) {
 var builds = []*Build{
 	{
 		Source:  true,
-		Builder: "linux-amd64",
+		Builder: "linux-amd64-jessie", // using Jessie for at least [Go 1.11, Go 1.13] due to golang.org/issue/31336
 	},
 	{
 		OS:      "linux",

dashboard/builders.go

@@ -1540,10 +1540,10 @@ func init() {
 		Notes: "Runs GOOS=linux but with the Android emulator attached, for running x/mobile host tests.",
 	})
 	addBuilder(BuildConfig{
-		Name:      "linux-amd64-stretch",
-		HostType:  "host-linux-stretch",
-		MaxAtOnce: 1,
-		Notes:     "Debian Stretch",
+		Name:      "linux-amd64-jessie",
+		HostType:  "host-linux-jessie",
+		MaxAtOnce: 5,
+		Notes:     "Debian Jessie. The normal 'linux-amd64' builder is stretch. We use Jessie for our release builds due to https://golang.org/issue/31293",
 		env: []string{
 			"GO_DISABLE_OUTBOUND_NETWORK=1",
 		},