Merge pull request #5613 from WnP/git-proxy #5904

Job	Run time
build (windows/amd64)	1m 54s
sandbox-build (linux/amd64)	7m 12s
build (freebsd/amd64)	1m 52s
sandbox-build (linux/arm64)	7m 9s
test-freebsd-amd64	3m 18s
test-windows-amd64 (containerd, ./client)	7m 49s
test-windows-amd64 (containerd, ./cmd/buildctl)	3m 1s
test-windows-amd64 (containerd, ./worker/containerd)	3m 45s
test-windows-amd64 (containerd, ./solver)	2m 36s
test-windows-amd64 (containerd, ./frontend)	1m 37s
test-windows-amd64 (containerd, ./frontend/dockerfile)	38m 11s
test-windows-amd64 (./..., 1)	4m 13s
	1h 22m 37s

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