tests: matrix with buildkit versions

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>

tests/integration.go

@@ -12,6 +12,8 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+const defaultBuildKitTag = "buildx-stable-1"
+
 func tmpdir(t *testing.T, appliers ...fstest.Applier) string {
 	t.Helper()
 	tmpdir := t.TempDir()
@@ -107,3 +109,10 @@ func isExperimental() bool {
 	}
 	return false
 }
+
+func buildkitTag() string {
+	if v := os.Getenv("TEST_BUILDKIT_TAG"); v != "" {
+		return v
+	}
+	return defaultBuildKitTag
+}

tests/integration_test.go

@@ -35,7 +35,7 @@ func TestIntegration(t *testing.T) {
 
 func testIntegration(t *testing.T, funcs ...func(t *testing.T, sb integration.Sandbox)) {
 	mirroredImages := integration.OfficialImages("busybox:latest", "alpine:latest")
-	buildkitImage := "docker.io/moby/buildkit:buildx-stable-1"
+	buildkitImage := "docker.io/moby/buildkit:" + buildkitTag()
 	if bkworkers.IsTestDockerd() {
 		if img, ok := os.LookupEnv("TEST_BUILDKIT_IMAGE"); ok {
 			ref, err := reference.ParseNormalizedNamed(img)