msbuild not embedding resource files

Hi,

I've a really strange problem that I thought was related to the vsts build vs solution task but I have been able to repro it on my end here too.

Basically I have a class library project targeting .net core 2, in the project there are a couple of TypeScript files I want to compile, and have the output of these files added as embedded resources to the generated dll.

Within VS 2017 on desktop all was ok, due to building/rebuilding but problem appeared on vsts when code was pulled down to a clean folder structure that contained no build outputs like js files or dlls. With a but of playing I was able to reproduce the behavior with a sample project.

Basically if you (from command line) do a solution clean and then a solution build, the js files will be generated but not added as embedded resources to the assembly.

The important bits of the csproj are as follows:
```

netcoreapp2.0
Library

```

In the sample solution there is a solution item domsbuild.cmd that issues the clean and build commands and if you look at the generated dll you will see no resources.

Using VS 2017 15.6.7
MSBuild.exe 15.6.85.37198

[EmbedResReproSol.zip](https://github.com/Microsoft/msbuild/files/1974791/EmbedResReproSol.zip)

Any ideas greatly appreciated