Fix to allow single-process on Linux. #16114

Job	Run time
linux-cobalt / initialize	1m 17s
linux-x64 / initialize	1m 15s
linux-x64 / docker-build-image	3m 43s
linux-cobalt / docker-build-image	3m 41s
linux-cobalt / x64_devel	24m 11s
linux-cobalt / x64_debug	25m 33s
linux-cobalt / x64_qa	25m 27s
linux-cobalt / x64_gold	28m 35s
linux-x64 / x64_devel	22m 50s
linux-x64 / x64_debug	29m 3s
linux-x64 / x64_qa	25m 58s
linux-x64 / x64_gold	30m 17s
	3h 41m 50s

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