build rofl: Fail if cannot connect to network

The current behavior silently falls back to production builds when your
Localnet is not accessible. If --mode is auto, then it should fail, when
the connection cannot be established.

cmd/rofl/build.go

@@ -71,14 +71,10 @@ var (
 			case buildMode == buildModeAuto && !offline:
 				ctx := context.Background()
 				conn, err := connection.Connect(ctx, npa.Network)
-				if err != nil {
-					break // Autodetection failed.
-				}
+				cobra.CheckErr(err)
 
 				params, err := conn.Consensus().Registry().ConsensusParameters(ctx, consensus.HeightLatest)
-				if err != nil {
-					break // Autodetection failed.
-				}
+				cobra.CheckErr(err)
 
 				if params.DebugAllowTestRuntimes {
 					buildMode = buildModeUnsafe