all: remove config for arm64 linaro builders

They've been decomissioned for some months now. Our arm64 builders are
on packet.net these days.

Change-Id: Iaede189157e0298812b2971cdd63599f6096d73d
Reviewed-on: https://go-review.googlesource.com/c/build/+/165781
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: bradfitz

cmd/buildlet/stage0/stage0.go

@@ -85,7 +85,7 @@ func main() {
 		}
 	case "linux/arm64":
 		switch env := os.Getenv("GO_BUILDER_ENV"); env {
-		case "host-linux-arm64-packet", "host-linux-arm64-linaro":
+		case "host-linux-arm64-packet":
 			// No special setup.
 		default:
 			panic(fmt.Sprintf("unknown/unspecified $GO_BUILDER_ENV value %q", env))
@@ -171,7 +171,7 @@ Download:
 		cmd.Args = append(cmd.Args, reverseHostTypeArgs("host-linux-s390x")...)
 	case "linux/arm64":
 		switch buildEnv {
-		case "host-linux-arm64-packet", "host-linux-arm64-linaro":
+		case "host-linux-arm64-packet":
 			hostname := os.Getenv("HOSTNAME") // if empty, docker container name is used
 			cmd.Args = append(cmd.Args,
 				"--reverse-type="+buildEnv,

dashboard/builders.go

@@ -402,15 +402,6 @@ var Hosts = map[string]*HostConfig{
 		SSHUsername:     "debian",
 		HermeticReverse: false, // TODO: use rundockerbuildlet like arm64
 	},
-	"host-linux-arm64-linaro": &HostConfig{
-		Notes:           "Ubuntu xenial; run by Go team, from linaro",
-		IsReverse:       true,
-		HermeticReverse: true,
-		ExpectNum:       5,
-		env:             []string{"GOROOT_BOOTSTRAP=/usr/local/go-bootstrap"},
-		ReverseAliases:  []string{"linux-arm64-buildlet"},
-		SSHUsername:     "root",
-	},
 	"host-linux-arm64-packet": &HostConfig{
 		Notes:           "On 96 core packet.net host (Xenial) in Docker containers (Jessie); run by Go team. See x/build/env/linux-arm64/packet",
 		IsReverse:       true,
@@ -1875,15 +1866,10 @@ func init() {
 		HostType: "host-linux-ppc64le-power9-osu",
 		FlakyNet: true,
 	})
-	addBuilder(BuildConfig{
-		Name:     "linux-arm64-buildlet",
-		HostType: "host-linux-arm64-linaro",
-		FlakyNet: true,
-	})
 	addBuilder(BuildConfig{
 		Name:     "linux-arm64-packet",
 		HostType: "host-linux-arm64-packet",
-		FlakyNet: true, // unknown; just copied from the linaro one
+		FlakyNet: true, // maybe not flaky, but here conservatively
 	})
 	addBuilder(BuildConfig{
 		Name:         "linux-mips",