build: add macoS Sierra builder

Change-Id: I10a7a9e44a158fdce5287a9b0b065b35d11fb502
Reviewed-on: https://go-review.googlesource.com/35470
Reviewed-by: Chris Broadfoot <cbro@golang.org>
diff --git a/cmd/makemac/makemac.go b/cmd/makemac/makemac.go
index 1bde87f..9e9c0a8a 100644
--- a/cmd/makemac/makemac.go
+++ b/cmd/makemac/makemac.go
@@ -10,7 +10,7 @@
 
 Usage:
 
-  $ makemac <osx_minor_version>  # e.g, 8, 9, 10, 11
+  $ makemac <osx_minor_version>  # e.g, 8, 9, 10, 11, 12
 
 */
 package main
@@ -89,7 +89,7 @@
 		guestType = "darwin12_64Guest"
 	case 9:
 		guestType = "darwin13_64Guest"
-	case 10, 11:
+	case 10, 11, 12:
 		guestType = "darwin14_64Guest"
 	default:
 		return fmt.Errorf("unsupported makemac minor OS X version %d", minor)
diff --git a/dashboard/builders.go b/dashboard/builders.go
index 70c5041..403226c 100644
--- a/dashboard/builders.go
+++ b/dashboard/builders.go
@@ -161,6 +161,14 @@
 		},
 		ReverseAliases: []string{"darwin-amd64-10_11"},
 	},
+	"host-darwin-10_12": &HostConfig{
+		IsReverse: true,
+		Notes:     "MacStadium OS X 10.12 VM under VMWare ESXi",
+		env: []string{
+			"GOROOT_BOOTSTRAP=/Users/gopher/go1.4",
+		},
+		ReverseAliases: []string{"darwin-amd64-10_12"},
+	},
 	"host-linux-s390x": &HostConfig{
 		Notes:          "run by IBM",
 		IsReverse:      true,
@@ -471,6 +479,7 @@
 	case "darwin-amd64-10_8",
 		"darwin-amd64-10_10",
 		"darwin-amd64-10_11",
+		"darwin-amd64-10_12",
 		"darwin-386-10_11",
 		"freebsd-386-gce101", "freebsd-amd64-gce101",
 		"linux-386", "linux-amd64", "linux-amd64-nocgo",
@@ -793,6 +802,10 @@
 		numTestHelpers:    2,
 		numTryTestHelpers: 3,
 	})
+	addBuilder(BuildConfig{
+		Name:     "darwin-amd64-10_12",
+		HostType: "host-darwin-10_12",
+	})
 
 	addBuilder(BuildConfig{
 		Name:  "android-arm-sdk19",