[scripts] can pass --batch mode to rpython from build script
[scripts] can pass --batch mode to rpython from build script

we'll need this for automated builds (e.g. travis ci)

cornell-brg/pydgin,futurecore/pydgin,cornell-brg/pydgin,futurecore/pydgin,cornell-brg/pydgin,futurecore/pydgin,cornell-brg/pydgin,futurecore/pydgin