cmd/{tailscale,tailscaled}: embed manifest into Windows binaries

This uses a go:generate statement to create a bunch of .syso files that
contain a Windows resource file. We check these in since they're less
than 1KiB each, and are only included on Windows.

Fixes #6429

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I0512c3c0b2ab9d8d8509cf2037b88b81affcb81f

cmd/mkmanifest/main.go

@@ -0,0 +1,52 @@
+// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// The mkmanifest command is a simple helper utility to create a '.syso' file
+// that contains a Windows manifest file.
+package main
+
+import (
+	"log"
+	"os"
+
+	"github.com/tc-hib/winres"
+)
+
+func main() {
+	if len(os.Args) != 4 {
+		log.Fatalf("usage: %s arch manifest.xml output.syso", os.Args[0])
+	}
+
+	arch := winres.Arch(os.Args[1])
+	switch arch {
+	case winres.ArchAMD64, winres.ArchARM64, winres.ArchI386, winres.ArchARM:
+	default:
+		log.Fatalf("unsupported arch: %s", arch)
+	}
+
+	manifest, err := os.ReadFile(os.Args[2])
+	if err != nil {
+		log.Fatalf("error reading manifest file %q: %v", os.Args[2], err)
+	}
+
+	out := os.Args[3]
+
+	// Start by creating an empty resource set
+	rs := winres.ResourceSet{}
+
+	// Add resources
+	rs.Set(winres.RT_MANIFEST, winres.ID(1), 0, manifest)
+
+	// Compile to a COFF object file
+	f, err := os.Create(out)
+	if err != nil {
+		log.Fatalf("error creating output file %q: %v", out, err)
+	}
+	if err := rs.WriteObject(f, arch); err != nil {
+		log.Fatalf("error writing object: %v", err)
+	}
+	if err := f.Close(); err != nil {
+		log.Fatalf("error writing output file %q: %v", out, err)
+	}
+}