AsmPrinter didn't directly represent the possibility of needing both
.eh_frame and .debug_frame, even though it is possible with
-force-dwarf-frame-section. Switch to representing it as bitflags, and
just cache the set of sections needed for the module rather than
handling the no-EH case specially.
It seems like this could all get moved to MachineFunction, especially
considering MachineFunction::needsFrameMoves should really be
referencing it, but there is some dependency on Function which prevents
that so I stopped here.