ProcessExecutor: do not modify mutable objects from parent in forked … #19721

Job	Run time
build_cmake (ubuntu:24.04, true, true)	3m 47s
build_cmake (alpine:3.23, false, false)	4m 25s
build_make (ubuntu:25.10)	2m 54s
build_make (ubuntu:24.04)	3m 17s
build_make (alpine:3.23)	5m 59s
build_cmake (ubuntu:25.10, true, true)	2m 55s
	23m 17s

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