dashboard: add linux-amd64-unified builder

This adds a trybot+builder for testing cmd/compile's unified IR
construction experiment on the dev.typeparams branch.

Fixes golang/go#46786.

Change-Id: Ibf3d5ab7a727c52cf13486798e02077faa08e2b5
Reviewed-on: https://go-review.googlesource.com/c/build/+/328891
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
diff --git a/dashboard/builders_test.go b/dashboard/builders_test.go
index 1cabe15..9666895 100644
--- a/dashboard/builders_test.go
+++ b/dashboard/builders_test.go
@@ -120,7 +120,7 @@
 		},
 		{
 			repo:   "go",
-			branch: "dev.link",
+			branch: "dev.typeparams",
 			want: []string{
 				"android-amd64-emu",
 				"freebsd-amd64-12_2",
@@ -128,6 +128,7 @@
 				"linux-386",
 				"linux-amd64",
 				"linux-amd64-race",
+				"linux-amd64-unified",
 				"linux-arm-aws",
 				"linux-arm64-aws",
 				"openbsd-amd64-68",
@@ -617,6 +618,13 @@
 		{b("linux-amd64-staticlockranking@go1.14", "go"), none},
 		{b("linux-amd64-staticlockranking", "net"), none},
 
+		{b("linux-amd64-unified", "go"), none},
+		{b("linux-amd64-unified", "tools"), none},
+		{b("linux-amd64-unified", "net"), none},
+		{b("linux-amd64-unified@dev.typeparams", "go"), both},
+		{b("linux-amd64-unified@dev.typeparams", "tools"), both},
+		{b("linux-amd64-unified@dev.typeparams", "net"), none},
+
 		{b("linux-amd64-noregabi", "go"), onlyPost},
 		{b("linux-amd64-noregabi", "net"), none},
 	}