std: retry waitid on EINTR in the pidfd wait path #218360

Job	Run time
Calculate job matrix	34s
PR - pr-check-1	35m 54s
PR - aarch64-gnu-llvm-21-2	38m 7s
PR - x86_64-gnu-miri	1h 20m 14s
PR - x86_64-gnu-next-trait-solver-polonius	57m 37s
PR - x86_64-gnu-llvm-21	1h 18m 44s
PR - x86_64-gnu-gcc	1h 5m 15s
PR - x86_64-gnu-gcc-core-tests	11m 59s
PR - tidy	5m 34s
PR - x86_64-gnu-tools	1h 1m 22s
PR - pr-check-2	42m 8s
PR - aarch64-gnu-llvm-21-1	1h 0m 10s
publish toolstate	0s
	8h 57m 38s

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