[build] Do not do process isolation on win or mac #4788

Job	Run time
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	33m 32s
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	14m 52s
pytorch_tutorial_build_worker (7, 15, linux.g5.4xlarge.nvidia.gpu)	21m 41s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	23m 12s
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	38m 18s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	17m 25s
pytorch_tutorial_build_worker (8, 15, linux.g5.4xlarge.nvidia.gpu)	15m 21s
pytorch_tutorial_build_worker (9, 15, linux.g5.4xlarge.nvidia.gpu)	14m 48s
pytorch_tutorial_build_worker (12, 15, linux.g5.4xlarge.nvidia.gpu)	27m 48s
pytorch_tutorial_build_worker (10, 15, linux.g5.4xlarge.nvidia.gpu)	16m 29s
pytorch_tutorial_build_worker (11, 15, linux.g5.4xlarge.nvidia.gpu)	17m 8s
pytorch_tutorial_build_worker (13, 15, linux.g5.4xlarge.nvidia.gpu)	19m 51s
pytorch_tutorial_build_worker (14, 15, linux.g5.4xlarge.nvidia.gpu)	37m 39s
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	21m 59s
pytorch_tutorial_build_worker (15, 15, linux.g5.4xlarge.nvidia.gpu)	26m 28s
pytorch_tutorial_build_manager	21m 57s
	6h 8m 28s

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