Update `,gitignore` (#15561)

[mono-project.git] / global.json

{
  "tools": {
    "dotnet": "3.0.100-preview6-012264"
  },
  "msbuild-sdks": {
    "Microsoft.DotNet.Arcade.Sdk": "1.0.0-beta.19330.1",
    "Microsoft.DotNet.Helix.Sdk": "2.0.0-beta.19330.1"
  }
}