Eliminate access of RubyBasicObject flags #533

Job	Run time
ruby-versions / Generate Ruby versions	4s
windows-latest 2.7	1m 38s
windows-latest 3.0	1m 4s
windows-latest 3.1	1m 8s
windows-latest mingw	1m 12s
windows-latest jruby-head	1m 41s
windows-latest 3.3	1m 2s
windows-latest 3.2	1m 4s
windows-latest mswin	1m 6s
windows-latest 3.4	1m 29s
	11m 28s

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