The Tor Browser / file revision

 var isWindows = ("@mozilla.org/windows-registry-key;1" in Components.classes);

 function get_test_program(prog)

 {

   var progPath = do_get_cwd();

   progPath.append(prog);

   if (isWindows)

     progPath.leafName = progPath.leafName + ".exe";

   return progPath;

 }

 function set_process_running_environment()

 {

   var envSvc = Components.classes["@mozilla.org/process/environment;1"].

     getService(Components.interfaces.nsIEnvironment);

   var dirSvc = Components.classes["@mozilla.org/file/directory_service;1"].

     getService(Components.interfaces.nsIProperties);

   var greDir = dirSvc.get("GreD", Components.interfaces.nsIFile);

   envSvc.set("DYLD_LIBRARY_PATH", greDir.path);

   // For Linux

   envSvc.set("LD_LIBRARY_PATH", greDir.path);

   //XXX: handle windows

 }