Fix compilation error with C23 #311

Job	Run time
ruby-versions / Generate Ruby versions	4s
ubuntu-20.04 2.3	36s
ubuntu-20.04 2.4	31s
ubuntu-20.04 2.5	36s
ubuntu-20.04 2.6	39s
ubuntu-20.04 2.7	35s
ubuntu-20.04 3.0	29s
ubuntu-20.04 3.1	35s
ubuntu-20.04 3.2	44s
ubuntu-20.04 3.3	34s
ubuntu-20.04 head	25s
ubuntu-20.04 jruby	1m 11s
ubuntu-20.04 jruby-head	1m 12s
ubuntu-22.04 2.3	48s
ubuntu-22.04 2.4	31s
ubuntu-22.04 2.5	35s
ubuntu-22.04 2.6	38s
ubuntu-22.04 2.7	39s
ubuntu-22.04 3.0	31s
ubuntu-22.04 3.1	33s
ubuntu-22.04 3.2	29s
ubuntu-22.04 3.3	34s
ubuntu-22.04 head	20s
ubuntu-22.04 jruby	1m 13s
ubuntu-22.04 jruby-head	1m 10s
macos-12 2.3	1m 7s
macos-12 2.4	1m 0s
macos-12 2.5	1m 20s
macos-12 2.6	1m 12s
macos-12 2.7	57s
macos-12 3.0	33s
macos-12 3.1	1m 5s
macos-12 3.2	33s
macos-12 3.3	42s
macos-12 head	36s
macos-12 jruby	57s
macos-12 jruby-head	1m 7s
macos-13 2.3	1m 3s
macos-13 2.4	1m 17s
macos-13 2.5	1m 15s
macos-13 2.6	1m 4s
macos-13 2.7	1m 6s
macos-13 3.0	1m 2s
macos-13 3.1	48s
macos-13 3.2	34s
macos-13 3.3	1m 7s
macos-13 head	45s
macos-13 jruby	1m 12s
macos-13 jruby-head	1m 37s
macos-14 2.6	51s
macos-14 2.7	44s
macos-14 3.0	39s
macos-14 3.1	26s
macos-14 3.2	19s
macos-14 3.3	21s
macos-14 head	17s
macos-14 jruby	57s
macos-14 jruby-head	45s
windows-latest 2.3	1m 49s
windows-latest 2.4	2m 38s
windows-latest 2.5	3m 8s
windows-latest 2.6	3m 11s
windows-latest 2.7	3m 41s
windows-latest 3.0	2m 37s
windows-latest 3.1	2m 24s
windows-latest 3.2	3m 32s
windows-latest 3.3	3m 37s
windows-latest head	2m 39s
windows-latest mswin	2m 43s
ubuntu-latest jruby-9.3	1m 0s
ubuntu-latest jruby-9.4	1m 15s
macos-latest truffleruby-head	42s
ubuntu-latest truffleruby-head	58s
	1h 21m 24s

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