client/windows integration tests: plumbing work for running on windows #2219

Job	Run time
prepare	9s
binaries (darwin/amd64)	58s
binaries (darwin/arm64)	1m 3s
binaries (linux/amd64)	2m 4s
binaries (linux/arm/v7)	2m 9s
binaries (linux/arm64)	2m 21s
binaries (linux/s390x)	2m 4s
binaries (linux/ppc64le)	2m 1s
binaries (linux/riscv64)	2m 6s
binaries (windows/amd64)	58s
binaries (windows/arm64)	58s
test / prepare	1m 38s
test / run (containerd, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	7m 4s
test / run (containerd-rootless, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integr...	8m 44s
test / run (containerd-1.6, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	6m 28s
test / run (containerd-snapshotter-stargz, ./client ./cmd/buildctl ./worker/containerd ./solver ./fronte...	8m 12s
test / run (oci, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	5m 32s
test / run (oci-rootless, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	5m 2s
test / run (oci-snapshotter-stargz, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, int...	5m 3s
test / run (./..., 1, integration gateway)	3m 53s
test / run (./client, containerd, nydus, integration)	7m 6s
test / run (./client, oci, nydus, integration)	4m 43s
test / run (./..., nydus, 1, integration)	3m 47s
image	7m 26s
image (rootless)	7m 32s
release	11s
	1h 39m 12s

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