Report mkfile metrics with --mk-metrics

Combined with roboleaf CI changes to pass this flag and subsequent
pipeline changes, this will allow basic mkfile metrics to be
dashboarded, which will help track mk2bp progress.

Bug: 217764943
Test: manual; verified mk_metrics.pb is generated iff --mk-metrics is
specified, used printproto on result

Change-Id: I348994b4d7e3479d0dc04de0276b94a702aac95b
diff --git a/ui/metrics/Android.bp b/ui/metrics/Android.bp
index 3ba3907..05db1d7 100644
--- a/ui/metrics/Android.bp
+++ b/ui/metrics/Android.bp
@@ -21,9 +21,10 @@
     pkgPath: "android/soong/ui/metrics",
     deps: [
         "golang-protobuf-proto",
+        "soong-ui-bp2build_metrics_proto",
         "soong-ui-metrics_upload_proto",
         "soong-ui-metrics_proto",
-        "soong-ui-bp2build_metrics_proto",
+        "soong-ui-mk_metrics_proto",
         "soong-ui-tracer",
         "soong-shared",
     ],
@@ -71,3 +72,15 @@
         "bp2build_metrics_proto/bp2build_metrics.pb.go",
     ],
 }
+
+bootstrap_go_package {
+    name: "soong-ui-mk_metrics_proto",
+    pkgPath: "android/soong/ui/metrics/mk_metrics_proto",
+    deps: [
+        "golang-protobuf-reflect-protoreflect",
+        "golang-protobuf-runtime-protoimpl",
+    ],
+    srcs: [
+        "mk_metrics_proto/mk_metrics.pb.go",
+    ],
+}