Eliminate access of RubyBasicObject flags #534

Job	Run time
ruby-versions / Generate Ruby versions	5s
windows-latest 3.2	1m 54s
windows-latest 3.0	1m 29s
windows-latest 2.7	2m 9s
windows-latest 3.3	1m 33s
windows-latest 3.4	1m 36s
windows-latest mingw	1m 22s
windows-latest 3.1	1m 37s
windows-latest jruby-head	2m 30s
windows-latest mswin	1m 33s
	15m 48s

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