ctfconvert should give more detail on DWARF errors
At present ctfconvert treats any DWARF error as an absence of type information. That's often not true, the lack of a CU, or a CU with no children indicates a lack of type information. However, a failure to fetch a CU, while nevertheless believing the file to contain DWARF data (libdwarf having been willing to init), tends to suggest present but badly formed DWARF. In this case, the precise error reported is invaluable.