{
  "sdk": {
    "version": "5.0.400",
    "rollForward": "latestFeature"
  }
}

{
  "sdk": {
    "version": "5.0.400",
    "rollForward": "latestFeature"
  },

  "additionalSdks": [
    "3.1.413"
  ]
}

Install .NET SDK 3.1 during build.
Install .NET SDK 3.1 during build.
