Tengo un proyecto .NET Core simple (aplicación de consola) que estoy tratando de compilar y ejecutar.dotnet build tiene éxito, pero obtengo el siguiente error cuando lo hagodotnet run:

λ dotnet run
Project RazorPrecompiler (.NETCoreApp,Version=v1.0) was previously compiled. Skipping compilation.
A fatal error was encountered. The library 'hostpolicy.dll' required to execute the application was not found in [path].

Mi project.json se ve así:

{
  "buildOptions": {
    "warningsAsErrors": true
  },
  "dependencies": {
    "Microsoft.AspNetCore.Razor": "1.0.0",
    "Microsoft.NETCore.App": {
      "type": "platform",
      "version": "1.0.0"
    }
  },
  "description": "Precompiles Razor views.",
  "frameworks": {
    "netcoreapp1.0": {
      "imports": [ ]
    }
  },
  "version": "1.2.0"
}

Que eshostpolicy.dll¿Y por qué falta?