dotnet-build will produce a deps file for portable builds, and will now
create "runnable" outputs for RID-less targets
the outputs won't actually be runnable today because we need corehost
changes and to generate a deps.json file for corehost to use.
Refactoring the MakeCompilationOutputRunnable code so that it is easier to move it to build. Making build stop passing runtime to compile. Moving the MakeCompilationOutputRunnable from compile to build.
Making WriteDepsFile create its directory if it does not exist.