[build] Provide in-tree llvm to mono correctly (#14607)

[mono-project.git] / global.json

{
  "tools": {
    "dotnet": "3.0.100-preview5-011568"
  },
  "msbuild-sdks": {
    "Microsoft.DotNet.Arcade.Sdk": "1.0.0-beta.19272.13",
    "Microsoft.DotNet.Helix.Sdk": "2.0.0-beta.19272.13"
  }
}