hack: use custom ref for buildkit tests

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

go.mod

@@ -55,7 +55,7 @@ require (
 	github.com/miekg/dns v1.1.66
 	github.com/mistifyio/go-zfs/v3 v3.0.1
 	github.com/mitchellh/copystructure v1.2.0
-	github.com/moby/buildkit v0.25.0-rc1
+	github.com/moby/buildkit v0.25.0-rc1 // TODO: remove custom ref in hack/buildkit-ref
 	github.com/moby/docker-image-spec v1.3.1
 	github.com/moby/go-archive v0.1.0
 	github.com/moby/ipvs v1.1.0

hack/buildkit-ref

@@ -19,6 +19,9 @@ if [[ "${buildkit_ref}" == *-*-* ]]; then
 	buildkit_ref=$(curl -s "https://api.github.com/repos/${buildkit_repo}/commits/${buildkit_ref}" | jq -r .sha)
 fi
 
+# Needed by v0.25.0-rc1
+buildkit_ref="e4d7acb44d7e29b594445a36c5cc28be44740142"
+
 cat << EOF
 BUILDKIT_REPO=$buildkit_repo
 BUILDKIT_REF=$buildkit_ref