tests: handle multiple docker versions

[crazy-max]

• needs testutil: add binary and extraEnv opt for dockerd worker moby/buildkit#4736

[crazy-max]

@tonistiigi As discussed we could also handle builders through docker context with specific dind image as follow-up.

[davhdavh]

These seem relevant to this pr:

buildx/tests/build.go

Lines 442 to 443 in 4327ee7

	// TODO: use stable buildkit image when v0.13.0 released
	out, err := createCmd(sb, withArgs("--driver", "docker-container", "--buildkitd-flags=--oci-worker-net=bridge --allow-insecure-entitlement=network.host", "--driver-opt", "image=moby/buildkit:v0.13.0-rc3"))

buildx/tests/build.go

Lines 576 to 577 in 4327ee7

	// TODO: use stable buildkit image when v0.13.0 released
	out, err := createCmd(sb, withArgs(

buildx/tests/build.go

Lines 643 to 644 in 4327ee7

	// TODO: use stable buildkit image when v0.13.0 released
	out, err := createCmd(sb, withArgs(

[crazy-max]

These seem relevant to this pr:

buildx/tests/build.go

Lines 442 to 443 in 4327ee7

	// TODO: use stable buildkit image when v0.13.0 released
	out, err := createCmd(sb, withArgs("--driver", "docker-container", "--buildkitd-flags=--oci-worker-net=bridge --allow-insecure-entitlement=network.host", "--driver-opt", "image=moby/buildkit:v0.13.0-rc3"))

buildx/tests/build.go

Lines 576 to 577 in 4327ee7

	// TODO: use stable buildkit image when v0.13.0 released
	out, err := createCmd(sb, withArgs(

buildx/tests/build.go

Lines 643 to 644 in 4327ee7

	// TODO: use stable buildkit image when v0.13.0 released
	out, err := createCmd(sb, withArgs(

WDYM? This PR is about testing multiple dockerd versions. For BuildKit see #2322