cmd/compile: refresh builtin.go

The export data format was augmented with a new "unsafe-uintptr" tag
in https://golang.org/cl/18584, but builtin.go was not regenerated.

While here, add a test to make sure builtin.go stays up to date in the
future.

Change-Id: I4ae17da29f0855bef6ec0fcc10e7082c8427d39c
Reviewed-on: https://go-review.googlesource.com/19681
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/cmd/compile/internal/gc/builtin_test.go

@@ -0,0 +1,31 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gc_test
+
+import (
+	"bytes"
+	"internal/testenv"
+	"io/ioutil"
+	"os/exec"
+	"testing"
+)
+
+func TestBuiltin(t *testing.T) {
+	testenv.MustHaveGoRun(t)
+
+	old, err := ioutil.ReadFile("builtin.go")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	new, err := exec.Command("go", "run", "mkbuiltin.go", "-stdout").Output()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !bytes.Equal(old, new) {
+		t.Fatal("builtin.go out of date; run mkbuiltin.go")
+	}
+}