anchor.diff:                        //yield "--optimize-" 
                         yield "--nooptimizationdata"
                         yield "--noframework"
  -                      if msCoreLib.IsSome then
  -                        yield sprintf "-r:%s" msCoreLib.Value
  +                      yield sprintf "-I:%s" sysDir
  +                      for ref in defaultReferences do
  +                        if not (hasAssembly ref) then
  +                          yield sprintf "-r:%s" (sysLib ref)
                         if fsCoreLib.IsSome then
                           yield sprintf "-r:%s" fsCoreLib.Value
                         yield "--out:" + dllName
  
positive.code:   module internal FSharpAssemblyHelper =
        open System.IO
        let checker = FSharpChecker.Create()
  
        let sysLib nm = 
            if System.Environment.OSVersion.Platform = System.PlatformID.Win32NT then // file references only valid on Windows 
                @"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\" + nm + ".dll"
            else
                let sysDir = System.Runtime.InteropServices.RuntimeEnvironment.GetRuntimeDirectory()
                let (++) a b = System.IO.Path.Combine(a,b)
                sysDir ++ nm + ".dll" 
  
        let fsCore4300() = 
            if System.Environment.OSVersion.Platform = System.PlatformID.Win32NT then // file references only valid on Windows 
  
negative.code:               sysLib "FSharp.Core"
  
        let getProjectReferences otherFlags libDirs dllFiles = 
            let dllFiles = dllFiles |> Seq.toList
            let hasAssembly asm = dllFiles |> Seq.exists (fun a -> Path.GetFileNameWithoutExtension a = asm)
            let hasFsCoreLib = hasAssembly "FSharp.Core"
            let fsCoreLib =
              if not hasFsCoreLib then Some (fsCore4300())
              else None
            let defaultReferences = [ "mscorlib"; "System"; "System.Core" ]
            let otherFlags = defaultArg otherFlags Seq.empty
            let libDirs = defaultArg libDirs Seq.empty
            let base1 = Path.GetTempFileName()
  