The include_compiler_rt stored in the bin file options means that we need
compiler-rt symbols *somehow*. However, in the context of using the stage1 backend
we need to tell stage1 to include compiler-rt only if stage1 is the place that
needs to provide those symbols. Otherwise the stage2 infrastructure will take care
of it in the linker, by putting compiler_rt.o into a static archive, or linking
compiler_rt.a against an executable. In other words we only want to set this flag
for stage1 if we are using build-obj.