README: add command for building enterprise binary (#7336)
README: add command for building enterprise binary (#7336)

* README: add command for building enterprise binary

* README: add warning about built-in license

hartsock/vault,kingland/vault,hashicorp/vault,rnaveiras/vault,quixoten/vault,quixoten/vault,hashicorp/vault,joelthompson/vault,rnaveiras/vault,hashicorp/vault,kingland/vault,hashicorp/vault,quixoten/vault,rnaveiras/vault,hartsock/vault,kingland/vault,hartsock/vault,quixoten/vault,joelthompson/vault,rnaveiras/vault,hartsock/vault,hartsock/vault,hashicorp/vault,hashicorp/vault,kingland/vault,kingland/vault,joelthompson/vault,joelthompson/vault,rnaveiras/vault