.NET team provides an MSBuild SDK that enables you to build projects written in Common Intermediate Language (.ilproj). It was previously used only internally in CoreCLR repository, but now it is published on NuGet and can be used by everyone: https://www.nuget.org/packages/Microsoft.NET.Sdk.IL. This example shows how to build a Hello World applciation in IL using this SDK. Example is based on instructions by @tannergooding in dotnet/runtime#11411.
To build this example, open a command line in the example directory and execute dotnet build.