Fix compilation error with C23 #314

Job	Run time
ruby-versions / Generate Ruby versions	4s
ubuntu-20.04 2.3	33s
ubuntu-20.04 2.4	35s
ubuntu-20.04 2.5	35s
ubuntu-20.04 2.6	51s
ubuntu-20.04 2.7	37s
ubuntu-20.04 3.0	32s
ubuntu-20.04 3.1	35s
ubuntu-20.04 3.2	28s
ubuntu-20.04 3.3	31s
ubuntu-20.04 head	21s
ubuntu-20.04 jruby	1m 10s
ubuntu-20.04 jruby-head	1m 9s
ubuntu-22.04 2.3	32s
ubuntu-22.04 2.4	32s
ubuntu-22.04 2.5	35s
ubuntu-22.04 2.6	36s
ubuntu-22.04 2.7	36s
ubuntu-22.04 3.0	29s
ubuntu-22.04 3.1	29s
ubuntu-22.04 3.2	29s
ubuntu-22.04 3.3	33s
ubuntu-22.04 head	26s
ubuntu-22.04 jruby	1m 7s
ubuntu-22.04 jruby-head	1m 12s
macos-12 2.3	1m 4s
macos-12 2.4	1m 2s
macos-12 2.5	1m 8s
macos-12 2.6	1m 34s
macos-12 2.7	1m 16s
macos-12 3.0	35s
macos-12 3.1	31s
macos-12 3.2	30s
macos-12 3.3	31s
macos-12 head	27s
macos-12 jruby	1m 0s
macos-12 jruby-head	1m 2s
macos-13 2.3	1m 9s
macos-13 2.4	1m 5s
macos-13 2.5	1m 22s
macos-13 2.6	1m 32s
macos-13 2.7	1m 35s
macos-13 3.0	52s
macos-13 3.1	56s
macos-13 3.2	50s
macos-13 3.3	33s
macos-13 head	26s
macos-13 jruby	1m 23s
macos-13 jruby-head	2m 16s
macos-14 2.6	1m 1s
macos-14 2.7	30s
macos-14 3.0	20s
macos-14 3.1	28s
macos-14 3.2	20s
macos-14 3.3	22s
macos-14 head	43s
macos-14 jruby	40s
macos-14 jruby-head	42s
windows-latest 2.3	2m 6s
windows-latest 2.4	2m 46s
windows-latest 2.5	3m 33s
windows-latest 2.6	2m 41s
windows-latest 2.7	2m 50s
windows-latest 3.0	2m 43s
windows-latest 3.1	3m 17s
windows-latest 3.2	3m 5s
windows-latest 3.3	3m 38s
windows-latest head	1m 26s
windows-latest mswin	2m 59s
ubuntu-latest jruby-9.3	1m 5s
ubuntu-latest jruby-9.4	1m 5s
macos-latest truffleruby-head	36s
ubuntu-latest truffleruby-head	1m 16s
	1h 20m 28s

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