fix dead forked pthread_fork children #4488

Job	Run time
prepare	12s
Build macOS arm64 binaries	32m 46s
Build macOS x86_64 binaries	36m 40s
Build linux/amd64 static musl binary (debug)	36m 35s
Build linux/arm64 static GNU binary	36m 35s
Build linux/arm64 static musl binary	23m 9s
Build linux/amd64 static GNU binary	36m 35s
Build linux/amd64 static musl binary (mimalloc)	36m 35s
Build linux/amd64 static musl binary	27m 32s
push	1s
	4h 26m 40s

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