Adding a 'just symlink to cgi-bin' nix-serve.cgi

Currently nix-serve as it is supposed to be run as a server. Add an option to use it as a CGI script with any HTTP server. The CGI can be just symlinked/copied to cgi-bin with zero configuration.
Hm, why is this needed? Doesn't Plack's CGI module handle CGI variables in a standard way?