LanguageServiceHost is not correctly resolving reference paths

1. Compile this via command-line and then open in VS

``` C#
using System;
using Accessibility;

namespace ConsoleApp1
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hello World!");
}
}
}
```

``` XML

Exe
netcoreapp1.1
c:\users\davkean\documents\visual studio 2017\Projects\ConsoleApp262\ConsoleApp262\obj\Debug

```

Expected: For it to be successfully compiled in both
Actual: Command-line compiles sucessfully, IntelliSense filter shows:

```
Severity Code Description Project File Line Suppression State
Error CS0246 The type or namespace name 'Accessibility' could not be found (are you missing a using directive or an assembly reference?) ConsoleApp1 c:\users\davkean\documents\visual studio 2017\Projects\ConsoleApp262\ConsoleApp1\Program.cs 2 Active
```