dashboard: split iOS builder in arm and arm64

The iOS builder is horribly slow. Speed it up by splitting the
single builder in two, one for arm and one for arm64.

Change-Id: Iabe5f305433c5c613b71712609a339dc2d6abc89
Reviewed-on: https://go-review.googlesource.com/57297
Reviewed-by: Sarah Adams <shadams@google.com>
diff --git a/dashboard/builders.go b/dashboard/builders.go
index 3709652..53948d9 100644
--- a/dashboard/builders.go
+++ b/dashboard/builders.go
@@ -395,8 +395,18 @@
 			"GOOS=android",
 		},
 	},
-	"host-darwin-amd64-eliasnaur-ios": &HostConfig{
-		Notes:       "Mac Mini hosted by Elias Naur, running the ios reverse buildlet",
+	"host-darwin-amd64-eliasnaur-ios-arm64": &HostConfig{
+		Notes:       "Mac Mini hosted by Elias Naur, running the arm64 ios reverse buildlet",
+		OwnerGithub: "eliasnaur",
+		IsReverse:   true,
+		ExpectNum:   1,
+		env: []string{
+			"GOROOT_BOOTSTRAP=/usr/local/go-bootstrap",
+			"GOHOSTARCH=amd64",
+		},
+	},
+	"host-darwin-amd64-eliasnaur-ios-arm": &HostConfig{
+		Notes:       "Mac Mini hosted by Elias Naur, running the arm ios reverse buildlet",
 		OwnerGithub: "eliasnaur",
 		IsReverse:   true,
 		ExpectNum:   1,
@@ -1122,15 +1132,15 @@
 		HostType: "host-darwin-10_12",
 	})
 	addBuilder(BuildConfig{
-		Name:     "darwin-arm-a1549ios",
-		HostType: "host-darwin-amd64-eliasnaur-ios",
-		Notes:    "iPhone 6 (model A1549), via a Mac Mini; owned by elias.naur",
+		Name:     "darwin-arm-a1428ios",
+		HostType: "host-darwin-amd64-eliasnaur-ios-arm",
+		Notes:    "iPhone 5 (model A1428), via a Mac Mini; owned by elias.naur",
 		env:      []string{"GOARCH=arm"},
 	})
 	addBuilder(BuildConfig{
-		Name:     "darwin-arm64-a1549ios",
-		HostType: "host-darwin-amd64-eliasnaur-ios",
-		Notes:    "iPhone 6 (model A1549), via a Mac Mini; owned by elias.naur",
+		Name:     "darwin-arm64-a1457ios",
+		HostType: "host-darwin-amd64-eliasnaur-ios-arm64",
+		Notes:    "iPhone 5s (model A1457), via a Mac Mini; owned by elias.naur",
 		env:      []string{"GOARCH=arm64"},
 	})
 	addBuilder(BuildConfig{