Xcode no longer distributes the PackageMaker tools. Add a deprecation warning when the generator is used.
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
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 (closed)