Apparmor 3.0.3 fails to build against Ruby 3.1

Originally reported downstream: https://bugzilla.opensuse.org/show_bug.cgi?id=1194221

Ruby 3.1 has been released in Dec 2021; trying to rebuild AppArmor against Ruby 3.1 fails though:

[   51s] creating Makefile
[   51s] extconf.rb:30:in `foreach': No such file or directory @ rb_sysopen - Makefile.new (Errno::ENOENT)
[   51s] 	from extconf.rb:30:in `block in <main>'
[   51s] 	from extconf.rb:10:in `block in open'
[   51s] 	from extconf.rb:10:in `open'
[   51s] 	from extconf.rb:10:in `open'
[   51s] 	from extconf.rb:29:in `<main>'
[   51s] make[2]: *** [Makefile:472: Makefile.ruby] Error 1
[   51s] make[2]: Leaving directory '/home/abuild/rpmbuild/BUILD/apparmor-3.0.3/libraries/libapparmor/swig/ruby'
[   51s] make[1]: *** [Makefile:376: all-recursive] Error 1
[   51s] make[1]: Leaving directory '/home/abuild/rpmbuild/BUILD/apparmor-3.0.3/libraries/libapparmor/swig'
[   51s] make: *** [Makefile:408: all-recursive] Error 1

Full build log available at https://build.opensuse.org/package/live_build_log/openSUSE:Factory:Staging:L/apparmor/standard/x86_64