tool/gocross: a tool for building Tailscale binaries

Signed-off-by: David Anderson <danderson@tailscale.com>

tool/gocross/exec_unix.go

@@ -0,0 +1,12 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build unix
+
+package main
+
+import "golang.org/x/sys/unix"
+
+func doExec(cmd string, args []string, env []string) error {
+	return unix.Exec(cmd, args, env)
+}