Change restartBuilder to return cleanly when already started

Basically, if the builder is in the 'created' state for example, and we
transition into 'started', there's no reason to start it.

internal/build/imgsrc/ensure_builder.go

@@ -65,7 +65,7 @@ func EnsureBuilder(ctx context.Context, org *fly.Organization, region string, re
 		}
 
 		if validateBuilderErr == BuilderMachineNotStarted {
-			err := restartBuilderMachine(ctx, builderMachine)
+			err := startBuilder(ctx, builderMachine)
 			switch {
 			case errors.Is(err, ShouldReplaceBuilderMachine):
 				span.AddEvent("recreating builder due to resource reservation error")
@@ -406,13 +406,21 @@ func createBuilder(ctx context.Context, org *fly.Organization, region, builderNa
 	return
 }
 
-func restartBuilderMachine(ctx context.Context, builderMachine *fly.Machine) error {
+func startBuilder(ctx context.Context, builderMachine *fly.Machine) error {
 	ctx, span := tracing.GetTracer().Start(ctx, "restart_builder_machine")
 	defer span.End()
 
 	flapsClient := flapsutil.ClientFromContext(ctx)
 
-	mach.WaitForAnyMachineState(ctx, builderMachine, []string{"started", "stopped"}, 60*time.Second, nil)
+	state, err := mach.WaitForAnyMachineState(ctx, builderMachine, []string{"started", "stopped"}, 60*time.Second, nil)
+	if err != nil {
+		tracing.RecordError(span, err, "error waiting for builder machine to start or stop")
+		return err
+	}
+
+	if state == "started" {
+		return nil
+	}
 
 	if err := flapsClient.Restart(ctx, fly.RestartMachineInput{
 		ID: builderMachine.ID,

internal/build/imgsrc/ensure_builder_test.go

@@ -285,13 +285,13 @@ func TestRestartBuilderMachine(t *testing.T) {
 	}
 
 	ctx = flapsutil.NewContextWithClient(ctx, &flapsClient)
-	err := restartBuilderMachine(ctx, &fly.Machine{ID: "bigmachine"})
+	err := startBuilder(ctx, &fly.Machine{ID: "bigmachine"})
 	assert.NoError(t, err)
 	assert.True(t, waitedForStartOrStop)
 
 	waitedForStartOrStop = false
 	couldNotReserveResources = true
-	err = restartBuilderMachine(ctx, &fly.Machine{ID: "bigmachine"})
+	err = startBuilder(ctx, &fly.Machine{ID: "bigmachine"})
 	assert.True(t, waitedForStartOrStop)
 	assert.Error(t, err)
 	assert.ErrorIs(t, err, ShouldReplaceBuilderMachine)