Add status messages for RBE and product config

RBE adds a lot of time to m nothing builds,
so add status messages for it so that it's not misattributed
to some other part of the build.

Bug: 269644490
Test: m nothing
Change-Id: Ifff11bfc88f43b559526f3e3d3022c1388e42156

ui/build/rbe.go

@@ -100,6 +100,8 @@ func startRBE(ctx Context, config Config) {
 	ctx.BeginTrace(metrics.RunSetupTool, "rbe_bootstrap")
 	defer ctx.EndTrace()
 
+	ctx.Status.Status("Starting rbe...")
+
 	if u := ulimitOrFatal(ctx, config, "-u"); u < rbeLeastNProcs {
 		ctx.Fatalf("max user processes is insufficient: %d; want >= %d.\n", u, rbeLeastNProcs)
 	}
@@ -180,6 +182,8 @@ func DumpRBEMetrics(ctx Context, config Config, filename string) {
 		return
 	}
 
+	ctx.Status.Status("Dumping rbe metrics...")
+
 	outputDir := config.rbeProxyLogsDir()
 	if outputDir == "" {
 		ctx.Fatal("RBE output dir variable not defined. Aborting metrics dumping.")