client/windows integration tests: plumbing work for running on windows #2259

Job	Run time
prepare	5s
binaries (darwin/amd64)	1m 0s
binaries (darwin/arm64)	1m 12s
binaries (linux/amd64)	2m 16s
binaries (linux/arm/v7)	2m 0s
binaries (linux/arm64)	2m 0s
binaries (linux/s390x)	2m 18s
binaries (linux/ppc64le)	2m 0s
binaries (linux/riscv64)	2m 3s
binaries (windows/amd64)	1m 12s
binaries (windows/arm64)	1m 10s
test / prepare	1m 55s
test / run (containerd, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	6m 46s
test / run (containerd-rootless, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integr...	8m 36s
test / run (containerd-1.6, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	7m 23s
test / run (containerd-snapshotter-stargz, ./client ./cmd/buildctl ./worker/containerd ./solver ./fronte...	8m 19s
test / run (oci, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	4m 56s
test / run (oci-rootless, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	5m 6s
test / run (oci-snapshotter-stargz, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, int...	5m 2s
test / run (./..., 1, integration gateway)	4m 1s
test / run (./client, containerd, nydus, integration)	7m 4s
test / run (./client, oci, nydus, integration)	5m 24s
test / run (./..., nydus, 1, integration)	3m 59s
image	7m 24s
image (rootless)	7m 34s
release	10s
	1h 40m 55s

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