Introduce new OpenRA.exe entrypoint and change OpenRA.Game to a library.

OpenRA.Launcher/App.config

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+<?xml version="1.0" encoding="utf-8" ?>
+<configuration>
+  <runtime>
+    <loadFromRemoteSources enabled="true" />
+  </runtime>
+</configuration>

OpenRA.Launcher/OpenRA.Launcher.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net472</TargetFramework>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <Optimize>true</Optimize>
+    <UseVSHostingProcess>false</UseVSHostingProcess>
+    <LangVersion>7.3</LangVersion>
+    <DebugSymbols>true</DebugSymbols>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+    <AutoGenerateBindingRedirects>false</AutoGenerateBindingRedirects>
+    <OutputPath>../bin</OutputPath>
+    <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
+    <PlatformTarget>AnyCPU</PlatformTarget>
+    <ExternalConsole>false</ExternalConsole>
+    <EnableDefaultCompileItems>false</EnableDefaultCompileItems>
+    <CodeAnalysisRuleSet>..\OpenRA.ruleset</CodeAnalysisRuleSet>
+    <Configurations>Release;Debug</Configurations>
+    <AssemblyName>OpenRA</AssemblyName>
+  </PropertyGroup>
+  <PropertyGroup>
+    <TargetPlatform Condition="$([MSBuild]::IsOsPlatform('Windows'))">win-x64</TargetPlatform>
+    <TargetPlatform Condition="$([MSBuild]::IsOsPlatform('Linux'))">linux-x64</TargetPlatform>
+    <TargetPlatform Condition="$([MSBuild]::IsOsPlatform('OSX'))">osx-x64</TargetPlatform>
+  </PropertyGroup>
+  <ItemGroup>
+    <!-- Work around an issue where Rider does not detect files in the project root using the default glob -->
+    <Compile Include="**/*.cs" Exclude="$(DefaultItemExcludes)" />
+  </ItemGroup>
+  <PropertyGroup Condition="'$(Configuration)' == 'Debug'">
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <Optimize>false</Optimize>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(TargetPlatform)' == 'win-x86'">
+    <Prefer32bit>true</Prefer32bit>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(RunConfiguration)' == 'Red Alert'">
+    <StartAction>Project</StartAction>
+    <StartArguments>Engine.EngineDir=".." Game.Mod=ra</StartArguments>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(RunConfiguration)' == 'Dune 2000'">
+    <StartAction>Project</StartAction>
+    <StartArguments>Engine.EngineDir=".." Game.Mod=d2k</StartArguments>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(RunConfiguration)' == 'Tiberian Dawn'">
+    <StartAction>Project</StartAction>
+    <StartArguments>Engine.EngineDir=".." Game.Mod=cnc</StartArguments>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(RunConfiguration)' == 'Tiberian Sun'">
+    <StartAction>Project</StartAction>
+    <StartArguments>Engine.EngineDir=".." Game.Mod=ts</StartArguments>
+  </PropertyGroup>
+  <ItemGroup>
+    <None Include="App.config" />
+    <ProjectReference Include="..\OpenRA.Game\OpenRA.Game.csproj" />
+    <AdditionalFiles Include="../stylecop.json" />
+    <AdditionalFiles Include="Properties/launchSettings.json" />
+  </ItemGroup>
+  <Target Name="DisableAnalyzers" BeforeTargets="CoreCompile" Condition="'$(Configuration)'=='Release'">
+    <!-- Disable code style analysis on Release builds to improve compile-time performance -->
+    <ItemGroup Condition="'$(Configuration)'=='Release'">
+      <Analyzer Remove="@(Analyzer)" />
+    </ItemGroup>
+  </Target>
+</Project>

OpenRA.Launcher/Program.cs

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+#region Copyright & License Information
+/*
+ * Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System;
+using System.Diagnostics;
+using System.Linq;
+
+namespace OpenRA.Launcher
+{
+	static class Program
+	{
+		[STAThread]
+		static int Main(string[] args)
+		{
+			if (Debugger.IsAttached || args.Contains("--just-die"))
+				return (int)Game.InitializeAndRun(args);
+
+			AppDomain.CurrentDomain.UnhandledException += (_, e) => ExceptionHandler.HandleFatalError((Exception)e.ExceptionObject);
+
+			try
+			{
+				return (int)Game.InitializeAndRun(args);
+			}
+			catch (Exception e)
+			{
+				ExceptionHandler.HandleFatalError(e);
+				return (int)RunStatus.Error;
+			}
+		}
+	}
+}

OpenRA.Launcher/Properties/launchSettings.json

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+{
+  "profiles": {
+    "Tiberian Dawn": {
+      "commandName": "Project",
+      "commandLineArgs": "Engine.EngineDir=\"..\" Game.Mod=cnc"
+    },
+    "Red Alert": {
+      "commandName": "Project",
+      "commandLineArgs": "Engine.EngineDir=\"..\" Game.Mod=ra"
+    },
+    "Dune 2000": {
+      "commandName": "Project",
+      "commandLineArgs": "Engine.EngineDir=\"..\" Game.Mod=d2k"
+    },
+    "Tiberian Sun": {
+      "commandName": "Project",
+      "commandLineArgs": "Engine.EngineDir=\"..\" Game.Mod=ts"
+    }
+  }
+}