Batchmode builds need better support

[mwalk-dev]

When doing a batchmode build I was getting tons of NREs from IL2CPPBuildPreprocessor line 29 because Monitor.Settings was null. I believe this is because in-editor, Monitor.Construct runs as a delayCall callback but the editor doesn't fire those callbacks in batchmode.

The workaround I'm using for now is to call Construct via reflection in my batchmode build script, but I think it should be a public method or the Monitor ctor should have an alternative approach for batchmode.