Add -amdgpu-spill-cfi-saved-regs to enable complete debug info even when
codegen would otherwise not spill the EXEC mask. This is a workaround
until a solution to describe the EXEC mask without spills is integrated
based on the new structurizer.
Support emitting eh_frame for debug-info even when the target does not
Extend MCAsmInfo to reflect whether a target opts in to the
heterogeneous DWARF extensions.