CPack: Deprecate OSXX11 generator

The CPack OSXX11 generator has not had any updates since 2011 except as
part of sweeping maintenance changes.  It also creates packages with a
OSXScriptLauncher binary that has only ppc and i386 architectures which
are not supported by Apple anymore.  Furthermore, the generator is not
even mentioned in our documentation.  Add a deprecation warning.

Fixes: #20235

Source/CPack/cmCPackOSXX11Generator.cxx

@@ -178,6 +178,9 @@ int cmCPackOSXX11Generator::PackageFiles()
 
 int cmCPackOSXX11Generator::InitializeInternal()
 {
+  cmCPackLogger(cmCPackLog::LOG_WARNING,
+                "The OSXX11 generator is deprecated "
+                "and will be removed in a future version.\n");
   cmCPackLogger(cmCPackLog::LOG_DEBUG,
                 "cmCPackOSXX11Generator::Initialize()" << std::endl);
   std::vector<std::string> path;