build

Fix compiler warnings #69

Job	Run time
Build on ruby-head-debug (debug)	2m 0s
fedora	2m 49s
ubuntu ruby-3.0	1m 1s
ubuntu ruby-2.6	1m 24s
ubuntu ruby-2.7	1m 21s
ubuntu ruby-3.1	1m 6s
macos ruby-2.6	1m 1s
ubuntu ruby-head	1m 15s
ubuntu ruby-3.4	1m 18s
ubuntu ruby-3.2	1m 4s
macos ruby-3.0	33s
ubuntu ruby-3.3	1m 6s
macos ruby-3.1	47s
macos ruby-3.3	43s
windows ruby-2.7	3m 4s
windows ruby-2.6	3m 14s
macos ruby-3.2	34s
macos ruby-head	33s
macos ruby-3.4	35s
windows ruby-3.2	2m 51s
windows ruby-head	2m 15s
windows ruby-3.0	2m 29s
windows ruby-3.1	2m 29s
macos ruby-2.7	58s
windows ruby-3.3	2m 30s
windows ruby-3.4	2m 23s
	41m 23s

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