https://github.com/dotnet/roslyn/issues/57347

BuildHelloWorld.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net5.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="3.11.0" />
    <PackageReference Include="Microsoft.NET.HostModel" Version="3.1.16" />
  </ItemGroup>

</Project>

Program.cs

using System;
using System.IO;
using System.Linq;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.NET.HostModel.AppHost;

Directory.CreateDirectory(@"C:\code\tmp\HelloWorld");

var compilation = CSharpCompilation.Create(null)
    .AddSyntaxTrees(SyntaxFactory.ParseSyntaxTree(@"System.Console.WriteLine(""Hello, World!"");"))
    .AddReferences(Directory.EnumerateFiles(@"C:\Program Files\dotnet\packs\Microsoft.NETCore.App.Ref\5.0.0\ref\net5.0", "*.dll")
        .Select(f => MetadataReference.CreateFromFile(f)));
    
var result = compilation.Emit(@"C:\code\tmp\HelloWorld\HelloWorld.dll");

foreach (var diagnostic in result.Diagnostics)
{
    Console.WriteLine(diagnostic);
}

HostWriter.CreateAppHost(
    appHostSourceFilePath: @"C:\Program Files\dotnet\packs\Microsoft.NETCore.App.Host.win-x64\5.0.11\runtimes\win-x64\native\apphost.exe",
    appHostDestinationFilePath: @"C:\code\tmp\HelloWorld\HelloWorld.exe",
    appBinaryFilePath: @"C:\code\tmp\HelloWorld\HelloWorld.dll");

File.WriteAllText(@"C:\code\tmp\HelloWorld\HelloWorld.deps.json", @"{
  ""runtimeTarget"": {
    ""name"": "".NETCoreApp,Version=v5.0"",
    ""signature"": """"
  },
  ""compilationOptions"": {},
  ""targets"": {
    "".NETCoreApp,Version=v5.0"": {
      ""HelloWorld/1.0.0"": {
        ""runtime"": {
          ""HelloWorld.dll"": {}
        }
      }
    }
  },
  ""libraries"": {
    ""HelloWorld/1.0.0"": {
      ""type"": ""project"",
      ""serviceable"": false,
      ""sha512"": """"
    }
  }
}");

File.WriteAllText(@"C:\code\tmp\HelloWorld\HelloWorld.runtimeconfig.json", @"{
  ""runtimeOptions"": {
    ""tfm"": ""net5.0"",
    ""framework"": {
      ""name"": ""Microsoft.NETCore.App"",
      ""version"": ""5.0.0""
    }
  }
}");