fix internal/machine package to build on darwin

internal/machine/network_darwin.go

@@ -0,0 +1,13 @@
+//go:build darwin
+
+package machine
+
+import (
+	"context"
+	"fmt"
+)
+
+// setupDockerNetwork is a stub for darwin.
+func (nc *networkController) setupDockerNetwork(ctx context.Context) error {
+	return fmt.Errorf("not supported on darwin")
+}