While reviewing the MSBuild resolution, I came across some undocumented behaviour which we should remove.

In particular, when compiling scripts using direct invocation of "fsc.exe" (e.g. without using VisualStudio or MSBuild or --noframework) we compute this:

        let outputDirectory = 
            match tcConfig.outputFile with 
            | Some(outputFile) -> tcConfig.MakePathAbsolute outputFile
            | None -> tcConfig.implicitIncludeDir

then add this as a DLL search location:

        ... Path.GetDIrectroyName(outputDirectory)

What does this do?

• With an explicit output file this searches the output directory, which is very strange behaviour in any case - why are we searching the output directory for dependencies!?
• Without an explicit output file this searches the directory above the script root directory, which is nuts.

Explicit compilation of scripts is relatively rare and in any case people shouldn't be relying on behaviour that deviates so much when an explicit output file is/isn't used. Let's just remove this.