Use message generation in downstream bazel builds

Signed-off-by: Michael Carroll <mjcarroll@intrinsic.ai>

Author: mjcarroll

BUILD.bazel

@@ -0,0 +1,61 @@
+load(
+    "@gz//bazel/skylark:build_defs.bzl",
+    "GZ_FEATURES",
+    "GZ_ROOT",
+    "GZ_VISIBILITY",
+    "gz_configure_header",
+    "gz_export_header",
+    "gz_include_header",
+)
+load(
+    "@gz//msgs/tools:gz_msgs_generate.bzl",
+    "gz_proto_library",
+    "gz_proto_factory",
+)
+
+package(
+    default_visibility = GZ_VISIBILITY,
+    features = GZ_FEATURES,
+)
+
+licenses(["notice"])  # Apache-2.0
+
+exports_files(["LICENSE"])
+
+protos = glob(["src/proto/gz/sim/private_msgs/*.proto"])
+
+# Create a library of our protobuf message files
+proto_library(
+    name = "gzsim_proto",
+    srcs = protos,
+    strip_import_prefix = "src/proto",
+    deps = [
+        GZ_ROOT + "msgs:gzmsgs_proto"
+    ]
+)
+
+gz_proto_library(
+  name = "gzsim_cc_proto",
+  proto_deps = [":gzsim_proto"],
+  deps = [
+    "@com_google_protobuf//:protobuf",
+    GZ_ROOT + "msgs:gzmsgs_cc_proto"
+  ]
+)
+
+gz_proto_factory(
+  name = "gzsim_proto_factory",
+  deps = [":gzsim_proto"],
+  cc_output = "RegisterMsgs.cc",
+  hh_output = "include/gz/sim/private_msgs/MessageTypes.hh"
+)
+
+cc_binary(
+  name = "test_executable",
+  srcs = ["test_executable.cc", "RegisterMsgs.cc", "include/gz/sim/private_msgs/MessageTypes.hh"],
+  includes = ["include"],
+  deps = [
+    ":gzsim_cc_proto",
+    GZ_ROOT + "msgs"
+  ]
+)

test_executable.cc

@@ -0,0 +1,6 @@
+#include <gz/sim/private_msgs/peer_control.pb.h>
+
+int main(int argc, char** argv)
+{
+  gz::sim::private_msgs::PeerControl msg;
+}