proto: Add support for Process.User's Any

To avoid:

  go run ./example.go
  go/config.pb.go:26:8: cannot find package "google/protobuf" in any of:
          /usr/lib/go/src/google/protobuf (from $GOROOT)
          /home/wking/.local/lib/go/src/google/protobuf (from $GOPATH)
  Makefile:31: recipe for target 'example' failed

The Dockerfile changes will compile Google's any.proto to Go and
install it in the GOPATH.  Unfortunately, the jsonpb rendering isn't
quite right, since it's spitting out:

  "user": {
    "type_url": "oci.LinuxUser",
    "value": "qAYBsAYBuAYFuAYG"
  },

When it should be spitting out [1]:

  "user": {
    "@type": "type.googleapis.com/oci.LinuxUser",
    "uid": 1,
    "gid": 1,
    "additionalGids": [
      5,
      6
    ]
  },

[1]: https://developers.google.com/protocol-buffers/docs/proto3#json

Signed-off-by: W. Trevor King <[email protected]>

Author: wking

proto/Dockerfile

@@ -13,5 +13,8 @@ RUN dnf install -y golang git hg bzr
 ENV GOPATH /gopath
 ENV GOBIN /usr/bin
 RUN go get -u github.com/golang/protobuf/{proto,protoc-gen-go}
+WORKDIR protobuf-${PROTO_VERSION}
+RUN protoc --go_out=${GOPATH} src/google/protobuf/any.proto
+WORKDIR /
 VOLUME /proto /output
 CMD bash /proto/run.sh

proto/example.go

@@ -8,6 +8,8 @@ import (
 
 	oci "./go/"
 	"github.com/golang/protobuf/jsonpb"
+	"github.com/golang/protobuf/proto"
+	google_protobuf "google/protobuf"
 )
 
 func main() {
@@ -21,12 +23,22 @@ func main() {
 		},
 	}
 
+	user := &oci.LinuxUser{Uid: 1, Gid: 1, AdditionalGids: []int32{5, 6}}
+	userBytes, err := proto.Marshal(user)
+	if err != nil {
+		log.Fatal(err)
+	}
+	s.Spec.Process.User = &google_protobuf.Any{
+		TypeUrl: "oci.LinuxUser",
+		Value:   userBytes,
+	}
+
 	marshaler := jsonpb.Marshaler{
 		EnumsAsString: true,
 		Indent:        "  ",
 	}
 
-	err := marshaler.Marshal(os.Stdout, s)
+	err = marshaler.Marshal(os.Stdout, s)
 	if err != nil {
 		log.Fatal(err)
 	}