Update gomod and vendor

vendor/github.com/moby/buildkit/frontend/frontend.go

@@ -0,0 +1,32 @@
+package frontend
+
+import (
+	"context"
+	"io"
+
+	"github.com/moby/buildkit/cache"
+	"github.com/moby/buildkit/client"
+	"github.com/moby/buildkit/client/llb"
+	"github.com/moby/buildkit/executor"
+	gw "github.com/moby/buildkit/frontend/gateway/client"
+	"github.com/moby/buildkit/solver/pb"
+	digest "github.com/opencontainers/go-digest"
+)
+
+type Frontend interface {
+	Solve(ctx context.Context, llb FrontendLLBBridge, opt map[string]string, inputs map[string]*pb.Definition) (*Result, error)
+}
+
+type FrontendLLBBridge interface {
+	Solve(ctx context.Context, req SolveRequest) (*Result, error)
+	ResolveImageConfig(ctx context.Context, ref string, opt llb.ResolveImageConfigOpt) (digest.Digest, []byte, error)
+	Exec(ctx context.Context, meta executor.Meta, rootfs cache.ImmutableRef, stdin io.ReadCloser, stdout, stderr io.WriteCloser) error
+}
+
+type SolveRequest = gw.SolveRequest
+
+type CacheOptionsEntry = gw.CacheOptionsEntry
+
+type WorkerInfos interface {
+	WorkerInfos() []client.WorkerInfo
+}