cmd/buildlet/stage0: support upcoming host-linux-arm64-linaro host type

host-linux-arm64-linaro is identical to host-linux-arm64-packet, at
least for now.

And remove the old arm64-linaro support. We took down those machines
and are reimaging them.

Change-Id: Ieef462debc9356aadd828863561cc161fd10d8d1
Reviewed-on: https://go-review.googlesource.com/40653
Reviewed-by: Sarah Adams <shadams@google.com>
diff --git a/cmd/buildlet/stage0/stage0.go b/cmd/buildlet/stage0/stage0.go
index 158886f..05ac24a 100644
--- a/cmd/buildlet/stage0/stage0.go
+++ b/cmd/buildlet/stage0/stage0.go
@@ -57,10 +57,11 @@
 			}
 		}
 	case "linux/arm64":
-		if os.Getenv("GO_BUILDER_ENV") == "host-linux-arm64-packet" {
-			// No setup currently.
-		} else {
-			initLinaroARM64()
+		switch env := os.Getenv("GO_BUILDER_ENV"); env {
+		case "host-linux-arm64-packet", "host-linux-arm64-linaro":
+			// No special setup.
+		default:
+			panic(fmt.Sprintf("unknown/unspecified $GO_BUILDER_ENV value %q", env))
 		}
 	case "linux/ppc64":
 		initOregonStatePPC64()
@@ -110,18 +111,19 @@
 		cmd.Args = append(cmd.Args, "--workdir=/data/golang/workdir")
 		cmd.Args = append(cmd.Args, legacyReverseBuildletArgs("linux-s390x-ibm")...)
 	case "linux/arm64":
-		if os.Getenv("GO_BUILDER_ENV") == "host-linux-arm64-packet" {
+		switch v := os.Getenv("GO_BUILDER_ENV"); v {
+		case "host-linux-arm64-packet", "host-linux-arm64-linaro":
 			hostname := os.Getenv("HOSTNAME") // if empty, docker container name is used
 			cmd.Args = append(cmd.Args,
-				"--reverse-type=host-linux-arm64-packet",
+				"--reverse-type="+v,
 				"--workdir=/workdir",
 				"--hostname="+hostname,
 				"--halt=false",
 				"--reboot=false",
 				"--coordinator=farmer.golang.org:443",
 			)
-		} else {
-			cmd.Args = append(cmd.Args, legacyReverseBuildletArgs("linux-arm64-buildlet")...)
+		default:
+			panic(fmt.Sprintf("unknown/unspecified $GO_BUILDER_ENV value %q", env))
 		}
 	case "linux/ppc64":
 		cmd.Args = append(cmd.Args, legacyReverseBuildletArgs("linux-ppc64-buildlet")...)
@@ -422,11 +424,6 @@
 	}
 }
 
-func initLinaroARM64() {
-	aptGetInstall("gcc", "strace", "libc6-dev", "gdb")
-	initBootstrapDir("/usr/local/go-bootstrap", "/usr/local/go-bootstrap.tar.gz")
-}
-
 func initOregonStatePPC64() {
 	aptGetInstall("gcc", "strace", "libc6-dev", "gdb")
 	initBootstrapDir("/usr/local/go-bootstrap", "/usr/local/go-bootstrap.tar.gz")