Merge pull request #686 from byroot/io-flush #670

Job	Run time
Ruby memcheck	49s
ruby-versions / Generate Ruby versions	7s
ubuntu-22.04 2.7	56s
ubuntu-22.04 3.0	32s
ubuntu-22.04 3.1	34s
ubuntu-22.04 3.2	31s
ubuntu-22.04 3.3	45s
ubuntu-22.04 head	1m 18s
ubuntu-22.04 jruby	1m 6s
ubuntu-22.04 jruby-head	1m 11s
macos-13 2.7	2m 17s
macos-13 3.0	36s
macos-13 3.1	45s
macos-13 3.2	31s
macos-13 3.3	48s
macos-13 head	30s
macos-13 jruby	1m 21s
macos-13 jruby-head	2m 14s
macos-14 2.7	51s
macos-14 3.0	24s
macos-14 3.1	51s
macos-14 3.2	26s
macos-14 3.3	22s
macos-14 head	21s
macos-14 jruby	55s
macos-14 jruby-head	44s
windows-latest 2.7	3m 13s
windows-latest 3.0	2m 31s
windows-latest 3.1	2m 30s
windows-latest 3.2	2m 14s
windows-latest 3.3	2m 24s
windows-latest head	1m 38s
windows-latest mswin	1m 44s
ubuntu-latest jruby-9.4	1m 10s
macos-latest truffleruby-head	45s
ubuntu-latest truffleruby-head	1m 49s
	41m 43s

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