Add bp2build_metrics

Through a .proto

Bug: 201539536
Test: m nothing
Test: {bp2build,mixed_{libc,droid}}.sh
Test: CI
Change-Id: I18d25eb8cd40c8a88d9ae79a85980b956194a0d4
diff --git a/ui/metrics/Android.bp b/ui/metrics/Android.bp
index 1590ab0..96f6389 100644
--- a/ui/metrics/Android.bp
+++ b/ui/metrics/Android.bp
@@ -23,6 +23,7 @@
         "golang-protobuf-proto",
         "soong-ui-metrics_upload_proto",
         "soong-ui-metrics_proto",
+        "soong-ui-bp2build_metrics_proto",
         "soong-ui-tracer",
     ],
     srcs: [
@@ -57,3 +58,15 @@
         "upload_proto/upload.pb.go",
     ],
 }
+
+bootstrap_go_package {
+    name: "soong-ui-bp2build_metrics_proto",
+    pkgPath: "android/soong/ui/metrics/bp2build_metrics_proto",
+    deps: [
+        "golang-protobuf-reflect-protoreflect",
+        "golang-protobuf-runtime-protoimpl",
+    ],
+    srcs: [
+        "bp2build_metrics_proto/bp2build_metrics.pb.go",
+    ],
+}