Omit localized versions of assemblies from the build output

With the latest msbuild you can simply put this into your .csproj file:

<PropertyGroup>
  <SatelliteResourceLanguages>en-US</SatelliteResourceLanguages>
</PropertyGroup>

See dotnet/sdk/issues/774

What you can do is add a target (here, I named it 'RemoveSatelliteAssemblies') to the msbuild .csproj project file, for example, at the end:

<Project...>
  ....
  <Target Name="RemoveSatelliteAssemblies" AfterTargets="ResolveAssemblyReferences">
    <ItemGroup>
        <ReferenceCopyLocalPaths Remove="@(ReferenceSatellitePaths)" />
    </ItemGroup>
  </Target>
</Project>

This target will run after the standard ResolveAssemblyReferences target (defined somewhere in a Microsoft.Common[something].targets file in the C:\Program Files (x86)\MSBuild directory or in the C:\Windows\Microsoft.Net directory - it depends on your Visual Studio / MsBuild setups and versions), and it will remove all reference satellite paths from the list of referenced paths marked as copy local (both ItemGroup names are also declared in the standard .targets file).