use multitargetting.

nukebuild/_build.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
     <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
     <RootNamespace></RootNamespace>
     <IsPackable>False</IsPackable>
@@ -36,9 +36,10 @@
     <None Include="..\GitVersion.yml" Condition="Exists('..\GitVersion.yml')" />
     <Compile Remove="Numerge/**/*.*" />
     <Compile Include="Numerge/Numerge/**/*.cs" />
-    <Compile Include="..\src\tools\MicroComGenerator\**\*.cs" />
-    <Compile Remove="..\src\tools\MicroComGenerator\bin\*.cs" />
-    <Compile Remove="..\src\tools\MicroComGenerator\obj\*.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\src\tools\MicroComGenerator\MicroComGenerator.csproj" />
   </ItemGroup>
 
 </Project>

src/tools/MicroComGenerator/MicroComGenerator.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
     <PropertyGroup>
         <OutputType>Exe</OutputType>
-        <TargetFramework>net6.0</TargetFramework>
+        <TargetFrameworks>net6.0;netcoreapp3.1</TargetFrameworks>
     </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="CommandLineParser" Version="2.8.0" />