Remove warning when generating $(arch)-fake.rb
This happens if BASERUBY is Ruby 3.4.
$ rm -f *-fake.rb && make test-precheck RUBYOPT=-w >/dev/null build/arm64-darwin24-fake.rb:28: warning: ::Ruby is reserved for Ruby 3.5
Remove warning when generating $(arch)-fake.rb
This happens if BASERUBY is Ruby 3.4.